KR20120070315A - Solar cell and method for manufacturing the same - Google Patents

Abstract

PURPOSE: A solar cell and a manufacturing method there are provided to improve efficiency of a solar cell by eliminating detects on a surface and vicinity of a substrate by plasma surface treatment and having stable combination. CONSTITUTION: Provided is a substrate(110) of a first conductive type. An emitter part(121) is located on a first side of a substrate and has a second conductive type which is opposite to the first conductive type. A first electrode is electrically connected to the emitter part. A protection part is passivation-processed by using plasma. The protection part is located on a second side of the substrate located on the opposite side of the first side of the substrate. A second electrode is selectively connected to the substrate through the protection part.

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, and the generated electron-hole pairs are separated into electrons and holes charged by the photovoltaic effect, respectively, and the electrons are n-type. It moves toward the semiconductor portion and holes move toward the p-type semiconductor portion. The transferred electrons and holes are collected by the different electrodes connected to the p-type semiconductor portion and the n-type semiconductor portion, respectively, and the electrodes are connected by a wire to obtain electric power.

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

According to one aspect of the present invention, there is provided a method of manufacturing a solar cell, including forming an emitter portion of a second conductivity type opposite to the first conductivity type on a first surface of a substrate having a first conductivity type. Exposing a second surface of the substrate opposite to one surface to plasma to passivate the second surface using the plasma, forming a protection portion on the second surface of the passivated substrate And forming a first electrode connected to the emitter part and a second electrode selectively connected to the substrate through the protection part.

In the passivation step, the plasma may be generated using ammonia (NH ₃ ) or nitrous oxide (N ₂ O).

The passivation treatment step may generate the plasma using a direct PECVD method.

In the passivation step, the plasma may be generated using a frequency of 13.56 MHz or 15 MHz.

The protective part may have a thickness of 100 nm to 200 nm.

The protecting part may be formed using silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiNxOy), or aluminum oxide (Al ₂ O ₃ ).

When the first conductivity type is p-type, the protecting part forming step may include forming the protecting part with aluminum oxide (Al ₂ O ₃ ).

When the first conductivity type is n-type, the protecting part forming step may be formed of silicon nitride (SiNx) or silicon oxynitride (SiNxOy).

The protecting part may be formed of silicon oxide (SiOx).

The method of manufacturing a solar cell according to the above feature may further include forming an anti-reflection portion on the emitter portion.

In the forming of the anti-reflection portion, the anti-reflection portion may be formed of silicon nitride (SiNx).

The anti-reflection portion may have a refractive index of 2.0 to 2.1.

The forming of the first electrode and the second electrode may include forming a first electrode pattern on the anti-reflection portion, forming a second electrode pattern on the protection portion, and selectively applying a laser beam to the second electrode pattern. And irradiating the substrate having the first electrode pattern and the second electrode pattern, wherein the first electrode pattern passes through the anti-reflective portion and passes through the anti-reflective portion. The first electrode may be formed in contact with the second electrode, and the second electrode pattern of the portion to which the laser beam is irradiated may pass through the protective part to selectively contact the substrate to form the second electrode.

The forming of the first electrode and the second electrode may include forming a first electrode pattern on the anti-reflective portion, selectively removing the protective portion to selectively expose the second surface of the substrate, and And forming a second electrode pattern on the exposed second surface of the substrate, and heat treating the substrate having the first electrode pattern and the second electrode pattern. The first electrode pattern penetrates the anti-reflective portion to contact the emitter portion to form the first electrode, and the second electrode pattern selectively contacts the two surfaces of the exposed substrate to form the second electrode. Can be.

In the forming of the first electrode pattern, a first paste is coated on the emitter part by screen printing and then dried to form the first electrode pattern. The forming of the second electrode pattern is a second paste different from the first paste. May be applied by screen printing and then dried to form the second electrode pattern.

The first paste may contain silver (Ag), and the second face may contain aluminum (Al).

According to another aspect of the present invention, a solar cell includes an emitter portion having a substrate of a first conductivity type, a second conductivity type disposed on a first surface of the substrate and opposite to the first conductivity type, and electrically connected to the emitter portion. A first electrode, a passivation process using a plasma, and a protection unit located on a second surface of the substrate, which is opposite to the first surface of the substrate, a first electrode connected to the emitter unit, and the protection unit And a second electrode selectively connected to the substrate through the second electrode.

According to this feature, defects located on and near the surface of the substrate are changed into stable bonds by the plasma surface treatment, so that the amount of charge loss due to the defect is reduced. Thus, the efficiency of the solar cell is improved.

1 is a partial perspective view of a solar cell according to an embodiment of the present invention.
FIG. 2 is an example of sectional drawing which cut | disconnected the solar cell shown in FIG. 1 along the II-II line.
3A to 3I are views sequentially showing an example of a method of manufacturing a solar cell according to one 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 of layers, films, panels, regions, etc., are exaggerated for clarity. 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. On the contrary, when a part is "just above" another part, there is no other part in the middle. Also, when a part is formed as "whole" on the other part, it means not only that it is formed on the entire surface (or the front surface) of the other part but also not on the edge part.

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

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

Referring to FIG. 1, one example of the solar cell 11 according to an exemplary embodiment of the present invention is an incident surface that is a surface of the substrate 110 and a substrate 110 to which light is incident (hereinafter, referred to as “front”). The emitter portion 121 positioned at the side, the anti-reflection portion 130 positioned on the emitter portion 121, and the surface of the substrate 110 which is the opposite side of the front surface of the substrate 110 (hereinafter referred to as 'rear'). ] The protection unit 190 positioned above, the front electrode unit 140 connected to the emitter unit 121, the rear electrode unit 150 located on the protection unit 190 and connected to the substrate 110, and the substrate ( And a plurality of back surface field portions 172 positioned selectively at the back of the 110.

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

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

Unlike FIGS. 1 and 2, in an alternative example, the front surface of the 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 also have an uneven surface.

As such, when the entire surface of the substrate 110 is textured, the incident area of the substrate 110 increases and the light reflectivity decreases due to a plurality of reflection operations due to unevenness, so that the amount of light incident on the substrate 110 is increased. As it increases, the efficiency of the solar cell 11 is improved.

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

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

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

When the emitter portion 121 has an n-type conductivity type, the emitter portion 121 may be formed by doping the substrate 110 with impurities of a pentavalent element, and conversely, when the emitter portion 121 has a p-type conductivity type, The dopant may be formed by doping the substrate 110 with impurities.

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 smoothly penetrates the anti-reflection portion 130, so that the front electrode 140 and emitter portion 121 is more stable and smoothly connected.

The anti-reflection portion 130 also converts defects, such as dangling bonds, present on and near the surface of the substrate 110 by the hydrogen (H) contained therein into stable bonds. A passivation function is performed 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 by the anti-reflection unit 130 is reduced.

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, and may be omitted as necessary.

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

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

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

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

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

Each front bus bar 142 collects the charges collected by the plurality of front electrodes 141 that intersect as well as the charges (for example, electrons) moving from the emitter unit 121, and moves them in a desired direction. The width of the bars 142 is greater than the width of each front electrode 141.

The plurality of front busbars 142 are connected to an external device and output the collected charges to the external device.

The front electrode part 140 including the plurality of front electrodes 141 and the plurality of front bus bars 142 is made of at least one conductive material such as silver (Ag). However, in alternative examples, the conductive material may be nickel (Ni), copper (Cu), aluminum (Al), tin (Sn), zinc (Zn), indium (In), titanium (Ti), gold (Au) and It may be at least one selected from the group consisting of a combination thereof, but may be made of other conductive materials.

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.

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

The protection unit 190 disposed on the rear surface of the substrate 110 may be formed of silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiOxNy), or aluminum oxide (Al ₂ O ₃ ).

In this example, before the protection unit 190 is formed on the rear surface of the substrate 110, the rear surface of the substrate 110 is a plasma (plasma) using ammonia (NH ₃ ) or nitrous oxide (N ₂ O). The back surface of the 110 is surface treated, whereby defects such as dangling bonds present in and near the back surface of the substrate 110 are turned into stable bonds. Therefore, since a passivation function is performed to reduce the disappearance of the charges moved toward the surface of the substrate 110 due to the plasma surface treatment, the defects are caused to occur at or near the surface of the substrate 110 by the defects. The amount of charge lost is reduced.

In the present example, the rear surface of the substrate 110 is changed to ammonia (NH ₃ ) or nitrous oxide (N ₂ O) into a plasma state by using plasma enhanced chemical vapor deposition (PECVD), and then ionized hydrogen. A passivation effect occurs in which (H) or oxygen (O) binds to a defect present on the rear surface of the substrate 110 and turns the defect into a stable bond. At this time, when using ammonia (NH ₃ ), the passivation effect is obtained by ionized hydrogen (H), and when using nitrous oxide (N ₂ O), the passivation effect is obtained by ionized oxygen (O).

In this example, in order to generate plasma with ammonia (NH ₃ ) or nitrous oxide (N ₂ O), a direct PECVD (direct PECVD) method of generating a plasma in a process chamber in which the substrate 110 is placed, and directly High frequency such as 13.56 MHz or 15 MHz is used in the PECVD method.

As described above, the protection unit 190 of the present example is positioned on the rear surface of the substrate 110 on which the passivation treatment in which defects are removed by plasma surface treatment is performed.

In this case, the protection unit 190 prevents the back surface of the passivated substrate 110 from being exposed to air, and oxygen in air and silicon (Si, Si) of the substrate 110 are combined to form hydrogen (H) or the like. It prevents damaging the passivation process by oxygen (O). In addition, since the protection unit 190 performs the passivation function of the rear surface of the substrate 110 by the hydrogen (H) contained in the film formation, the rear surface passivation effect of the substrate 110 is further improved.

That is, in this example, the protection unit 190 protects the rear surface of the substrate 110 by plasma surface treatment, additionally performs a passivation function, and reflects the light passing through the substrate 110 toward the substrate 110. The amount of light incident on the substrate 110 is increased.

The thickness of the protection part 190 has a thickness of about 100 nm to about 200 nm.

In general, silicon nitride (SiNx) and silicon oxynitride (SiOxNy) have positive fixed charge characteristics, and aluminum oxide (Al ₂ O ₃ ) has a negative fixed charge ( negative fixed charge).

Therefore, when the substrate 110 has a p-type conductivity type, the protection unit 190 is made of aluminum oxide ((Al ₂ O ₃ ) having negative fixed charge characteristics, and the substrate 110 is n In the case of the conductive type, the protection unit 190 is formed of silicon nitride (SiNx) or silicon oxynitride (SiOxNy), which has positive fixed charge characteristics, and the charge from the substrate 110 to the rear electrode 150. It is more advantageous to improve the transmission efficiency.

That is, when the substrate 110 has a p-type conductivity type, when the protection unit 190 exhibits negative charge characteristics, holes that are positive charges moving toward the protection unit 190 may be separated from the protection unit 190. Since it has the opposite polarity, the polarity of the protection unit 190 is pulled toward the protection unit 190, while electrons, which are negative charges having the same polarity as the protection unit 190, are connected to the polarity of the protection unit 190. It is pushed to the opposite side of the protective part 190. In the same principle, when the substrate 110 has an n-type conductivity type, when the protection unit 190 exhibits both charge characteristics, electrons moving toward the protection unit 190 are transferred by the protection unit 190. Pulled toward the protection unit 190, the hole is pushed to the opposite side of the protection unit 190 by the protection unit 190.

Therefore, when the substrate 110 is p-type, when the protective part 190 is formed of silicon nitride (SiNx) or silicon oxynitride (SiNx), the amount of movement of holes moving from the substrate 110 to the back electrode part 150. Is further increased, and when the substrate 110 is n-type, when the protection unit 190 is formed of aluminum oxide (Al ₂ O ₃ ), the amount of electrons moving from the substrate 110 to the rear electrode 150 is Is increased more. In addition, as described above, as the protection unit 190 is formed of a material considering fixed charges according to the conductivity type of the substrate 110, the movement of unwanted charges from the substrate 110 toward the protection unit 190 may be more efficiently performed. As a result, the recombination amount of the charge becomes lower.

The plurality of backside electric fields 172 disposed on the backside of the substrate 110 are, for example, p + regions in which impurities of the same conductivity type as the substrate 110 are impurity portions doped at a higher concentration than the substrate 110.

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

The rear electrode 150 is disposed on the protection unit 190 and includes a plurality of rear bus bars 152 connected to the conductive layer 155 for the rear electrode and the conductive layer 155 for the rear electrode.

The conductive layer 155 for the rear electrode is disposed on the portion of the protective portion 190 except for the portion of the protective portion 190 in which the plurality of rear bus bars 152 are disposed. However, in an alternative example, the conductive layer 155 for the back electrode may not be located at the edge portion of the rear surface of the substrate 110.

The conductive layer 155 for the rear electrode includes a plurality of rear electrodes 151 connected to the plurality of rear electric fields 172 positioned on the substrate 110 through the protection unit 190.

As illustrated in FIG. 1, the plurality of rear electrodes 151 are connected to the substrate 110 in various shapes such as circular, elliptical, or polygonal at regular intervals, for example, about 0.5 mm to about 1 mm. However, in an alternative example, each rear electrode 151 may have a stripe shape extending in one direction while being electrically connected to the substrate 110, such as the front electrode 141. In this case, the number of back electrodes is much smaller than the number of back electrodes having a circular, elliptical or polygonal shape.

The back electrode 151 collects charges, for example, holes moving from the side of the substrate 110, and transfers the charges to the conductive layer 155 for the back electrode.

In this case, since the plurality of rear electric field parts 172 and the plurality of rear electrodes 151 having higher conductivity than the substrate 110 are in contact with each other due to a higher impurity concentration than the substrate 110, the plurality of rear electrodes (from the substrate 110) may be contacted. The charge mobility to 151 is improved.

The back electrode conductive layer 155 is made of a conductive material such as aluminum (Al), but is not limited thereto.

Thus, in an alternative example, the conductive layer 155 for the back electrode is nickel (Ni), copper (Cu), silver (Ag), tin (Sn), zinc (Zn), indium (In), titanium (Ti). At least one selected from the group consisting of gold (Au) and combinations thereof, or may be made of other conductive materials.

The plurality of rear electrodes 151 in contact with the substrate 110 may include only the components of the conductive layer 155 for the rear electrode or may not only include the components of the conductive layer 155 for the rear electrode, but also the protection unit 190 and the substrate 110. The components of are mixed.

As described above, the thickness of the protective part 190 disposed under the conductive layer 155 for the rear electrode is about 100 nm to 200 nm.

In this case, when the thickness of the protective part 190 is less than about 100 nm, the rear electrode is formed by a glass frit contained in a paste for the conductive layer 155 for the rear electrode positioned on the protective part 190. In the heat treatment for the conductive layer 155, the protection part 190 may be penetrated by the paste. In this case, a metal component such as aluminum (Al) contained in the paste may be combined with the silicon of the substrate 110. In addition, the passivation treatment by the plasma surface treatment may be damaged, and when the thickness of the protection part 190 exceeds about 200 nm, the time for forming the protection part 190 is increased to produce the solar cell 11. Efficiency may decrease and manufacturing costs may increase.

Therefore, when the thickness of the protection unit 190 is about 100 nm or more, damage to the protection unit 190 by the conductive layer 155 for the rear electrode is prevented and a more efficient passivation effect is obtained, and the protection unit 190 When the thickness is about 200 nm or less, the passivation effect and the production efficiency of the solar cell 11 can be improved more efficiently without increasing the manufacturing cost of the unnecessary solar cell 11.

The plurality of rear busbars 152 connected to the rear electrode conductive layer 155 are positioned on the protection unit 190 where the rear electrode conductive layer 155 is not located, and is the same as the front bus bar 142. It extends in the direction and has a stripe shape. In this case, the plurality of rear bus bars 152 face the front bus bar 142 with respect to the substrate 110.

The plurality of rear bus bars 152 collects charges transferred from the conductive layer 155 for the rear electrode, similar to the plurality of front bus bars 142. Accordingly, the plurality of rear bus bars 152 may be made of a material having a better conductivity than the conductive layer 155 for the rear electrode. For example, it contains at least one conductive material such as silver (Ag). However, in an alternative example, the plurality of rear busbars 152 may be nickel (Ni), copper (Cu), aluminum (Al), tin (Sn), zinc (Zn), indium (In), titanium (Ti). , Gold (Au) and combinations thereof, or at least one selected from the group consisting of a conductive material other than.

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

Unlike FIG. 1, in another example, the plurality of rear busbars 152 may partially overlap the conductive layer 155 for adjacent rear electrodes. In this case, since the area in contact with the conductive layer 155 for the rear electrode is increased and the contact resistance is reduced, the amount of charge transferred from the conductive layer 155 for the rear electrode to the plurality of rear busbars 152 is increased. . In addition, the conductive layer 155 for the rear electrode may be positioned on the protection unit 190 in which the rear bus bar 152 is positioned. In this case, the plurality of rear bus bars 152 may be disposed around the substrate 110. It is located on the conductive layer 155 for the rear electrode facing the front bus bar 142 of the corresponding. In this case, since the rear electrode conductive layer 155 is positioned on the protection unit 190 regardless of the formation position of the plurality of rear bus bars 152, the process of forming the conductive layer 155 for the rear electrode becomes easier. .

Further, in an alternative example, each of the rear electrode busbars 152 is a plurality of conductors of circular, elliptical or polygonal shape arranged at regular or irregular intervals along the extension direction of each front busbar 142 instead of a stripe shape. Can be done. In this case, the consumption of expensive materials such as silver (Ag) for the back electrode bus bar 152 is reduced, thereby reducing the manufacturing cost of the solar cell 11.

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

The solar cell 11 according to the present exemplary embodiment having the above structure has a plasma surface treatment on the back surface of the substrate 110 to reduce recombination of charges due to defects present on the surface of the substrate 110. The operation is as follows.

When light is irradiated onto the solar cell 11 and incident to the substrate 110 of the semiconductor through the antireflection unit 130 and the emitter unit 121, electron-hole pairs are generated in the substrate 110 of the semiconductor by light energy. . At this time, the reflection loss of the light incident on the substrate 110 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 front electrode 141 and the front bus bar 142, transferred to the front bus bar 142, and the holes moved toward the substrate 110 are adjacent to each other. After being delivered to the rear electrode 151, it is collected by the rear busbar 152. When the front bus bar 142 and the rear bus bar 152 are connected with a conductive wire, a current flows, which is used as power from the outside.

At this time, the back surface of the substrate 110 is subjected to the passivation function by the plasma treatment and protection unit 190 of ammonia (NH ₃ ) or nitrous oxide (N ₂ O), and at the back and the vicinity of the substrate 110. The amount of charge loss due to defects such as dangling bonds is reduced.

Next, an example of a method of manufacturing the solar cell 11 according to one embodiment of the present invention will be described with reference to FIGS. 3A to 3I.

First, as illustrated in FIG. 3A, a material containing a pentavalent element or a trivalent element impurity in a crystalline semiconductor substrate 110 made of single crystal or polycrystalline silicon or the like is doped into the substrate 110 by a thermal diffusion method, or the like. An emitter portion 121 is formed at 110. 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 etching process is performed to etch an oxide containing phosphorous (PSG) or an oxide containing boron (boron silicate glass, BSG) generated as the p-type impurity or the n-type impurity diffuses into the substrate 110. Remove through.

If necessary, before forming the emitter portion 121, the entire surface of the substrate 110 may be tested 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 illustrated in FIG. 3B, an emitter portion formed on the front surface of the substrate 110 using a film formation method such as plasma enhanced chemical vapor deposition (PECVD) or chemical vapor deposition (CVD). An anti-reflection portion 130 is formed on the 121. In this case, the anti-reflection unit 130 may have a refractive index of 2.0 to 2.1, and may be made of silicon nitride (SiNx) having a thickness of about 70 nm to 80 nm.

Next, as shown in FIG. 3C, a part of the rear surface of the substrate 110 is removed by wet etching or dry etching, and the emitter unit 121 formed on the rear surface of the substrate 110 is removed.

Next, as shown in FIG. 3D, ammonia (NH ₃ ) or nitrous oxide (N ₂ O) injected into the process chamber by PECVD is converted into a plasma state, and ionized hydrogen (H) or oxygen (O) is converted into a substrate. A passivation function is performed to combine defects such as dangling bonds present on the rear surface of 110 to convert the defects into stable bonds.

At this time, the PECVD method uses a high frequency method using a high frequency of 13.56 MHz or 15 MHz, and performs plasma surface treatment using a direct PECVD method in which plasma is generated in the process chamber itself in which the substrate 110 is placed.

In the case of remote PECVD, in which PECVD is performed by receiving plasma generated in an external process chamber separately from the process chamber in which the substrate 110 is placed, the plasma is introduced into the process chamber in which the substrate 110 is placed. The energy of the plasma decreases, and thus, the plasma introduced from the external process chamber into the process chamber in which the substrate 110 is placed has lower energy than the plasma generated directly in the process chamber placed in the substrate 110.

Therefore, the passivation treatment of the back surface of the substrate 110 by PECVD method is superior to the passivation process by the remote PECVD method.

That is, in general, when the surface of the substrate 110 is exposed to air, a silicon oxide film SiO ₂ is formed on the surface of the substrate 110 by oxygen in the air. At this time, since the silicon oxide film SiO ₂ is formed on the surface of the substrate 110 where the defect exists, the silicon oxide film SiO ₂ may not be changed into a stable bond during passivation. Thus, a silicon oxide film (SiO ₂₎ of a naturally produced (nature SiO ₂ layer) is the cause of reducing the passivation during the passivation treatment effect.

Therefore, when using the direct PECVD method having a larger plasma energy than the remote PECVD method, the etching amount of the silicon oxide film (SiO ₂ ), which is an obstacle to the passivation effect, is increased by the plasma. When used, the passivation effect is increased.

The ions or electrons present in the substrate 110 move in synchronization with the plasma movement state due to the movement of the generated plasma. This phenomenon is referred to as plasma resonance phenomenon. However, using a high frequency of 13.56 MHz or 15 MHz, the ions or electrons in the substrate 110 are much faster than the ions or electrons of the substrate 110 than the low frequency (eg 55 kHz). Can't easily follow movement Therefore, when using a high frequency than when using a low frequency, the plasma resonance phenomenon of ions or electrons existing in the substrate 110 is less likely to occur. In general, as the plasma resonance increases, ions or electrons in the substrate 110 easily receive energy from the plasma, thereby increasing the degree of excitation of ions or electrons in the substrate 110. The excitation phenomenon of ions or electrons causes damage to the surface of the substrate 110, which causes another defect on the surface of the substrate 110.

Therefore, when plasma is generated by using a low frequency than when using a high frequency, the surface of the substrate 110 is further damaged by plasma resonance, and the passivation is not performed completely by the plasma surface treatment. Occurs.

However, in this example, since the plasma resonance phenomenon that causes the defect of the new substrate 110 is minimized by using the high frequency, the passivation treatment by the plasma surface treatment is perfectly performed.

As described above, when plasma treatment of the rear surface of the substrate 110 by direct PECVD using a high frequency, hydrogen (H) is more reactive (binding force) than nitrogen (N) when ammonia (NH ₃ ) is used as the plasma source gas. Because of this, the passivation function is performed by the ionized hydrogen (H), and the passivation function is performed by the ionized oxygen (O) when nitrous oxide (N ₂ O) is used as the source gas.

Thus, by the plasma treatment on the backside of the substrate 110 as described above, defects present on the backside of the substrate 110 are changed into a stable bond.

Next, as shown in FIG. 3E, the protection part 190 is formed on the back surface of the plasma-treated substrate 110 by various film formation methods such as PECVD.

In this case, the protection unit 190 may have a thickness of about 100 nm to 200 nm, and silicon oxide (SiOx), silicon oxynitride (SiNx), silicon oxynitride (SiOxNy), or aluminum oxide (Al ₂ O ₃ ). It may be made of.

The protection unit 190 prevents the back surface of the plasma surface-treated substrate 110 from being exposed to air, thereby reducing the passivation effect by oxygen in the air, and producing a natural silicon oxide film (SiO ₂ ). Is prevented.

In addition, since the passivation function of the rear surface of the substrate 110 is further performed by hydrogen (H) contained in the protection unit 190, the passivation effect of the rear surface of the substrate 110 is further improved. Thus, the amount of charge lost by the defect is further reduced.

At this time, the substrate 110 is p be of the case, negative (-) when the protection unit 190 is formed of aluminum oxide (Al ₂ O ₃₎ having a fixed electric charge of a fixed charge of aluminum oxide (Al ₂ O ₃₎ ( Holes are pulled toward the rear surface of the substrate 110 and electrons are pushed toward the front surface of the substrate 110, thereby reducing charge recombination at the rear surface of the substrate 110 and moving toward the rear surface of the substrate 110. The amount of holes made increases.

Similarly, when the substrate 110 is n-type, when the protection unit 190 is formed of silicon nitride (SiNx) or silicon oxynitride (SiOxNy) having a positive fixed charge, the substrate may be formed by positive fixed charge. Electrons are pulled toward the rear surface of the substrate 110 and holes are pushed toward the front surface of the substrate 110, so that charge recombination at the rear surface of the substrate 110 is reduced, and the amount of electron movement toward the rear surface of the substrate 110 is increased.

In this example, in the case of forming the protection unit 190 after passivating the rear surface of the substrate 110 using ammonia (NH ₃ ) or oxygen nitrite (N ₂ O), the protection unit 190 after the plasma surface treatment The plasma evacuation process is performed before the formation, so that the plasma gas does not adversely affect the film quality or the physical characteristics of the protection unit 190. Therefore, in the present example, instead of performing the plasma surface treatment and the protection unit 190 by using a separate process chamber, the plasma treatment and the protection unit 190 are formed in one process. This reduces the manufacturing cost and manufacturing time of the solar cell 11.

Then, as shown in Figure 3f, by using a screen printing method, a paste containing silver (Ag) is applied to the corresponding portion of the anti-reflection portion 130 and dried at about 120 ℃ to about 200 ℃ The front electrode part pattern 40 is formed. The front electrode portion pattern 40 includes a front electrode pattern portion 41 and a front bus pattern portion 42 extending in directions crossing each other.

Next, as shown in FIG. 3G, by using a screen printing method, a paste containing aluminum (Al) is applied on the corresponding portion of the protection unit 190, and then dried at about 120 ° C. to about 200 ° C. to conduct the back electrode. The layer pattern 55 is formed.

Next, as illustrated in FIG. 3H, a paste containing silver (Ag) is applied onto the corresponding portion of the protection unit 190 using a screen printing method, followed by drying to form a plurality of rear busbar patterns 52. . In this case, unlike FIG. 3H, the plurality of rear busbar patterns 52 may be disposed on a portion of the adjacent rear electrode conductive layer pattern 55 and partially overlap the rear electrode conductive layer pattern 55.

In this embodiment, each of the rear busbar patterns 52 has a stripe shape extending in one direction, but, alternatively, circular, elliptical, or polygonal patterns may be arranged at regular or irregular intervals in one direction.

The order of forming the front electrode pattern 40, the conductive layer pattern 55 for the rear electrode, and the rear busbar pattern 52 can be changed.

Next, as shown in FIG. 3I, when the laser beam is selectively irradiated to a predetermined portion of the conductive layer pattern 55 for the rear electrode, the conductive layer pattern 55 for the rear electrode, the protective part 190 and the substrate thereunder. A molten mixture 153 in which the 110 is mixed with each other is formed. In an alternative example, when each back electrode has a stripe shape, the irradiation area of the laser beam also has a stripe shape extending in a predetermined direction.

At this time, the wavelength and intensity of the laser beam is determined according to the material, thickness, or the like of the conductive layer pattern 55 for the rear electrode and the protective part 190 thereunder.

Then, the substrate 110 on which the conductive layer pattern 55 for the rear electrode, the plurality of rear busbar patterns 52 and the front electrode part pattern 40 are formed is fired at a temperature of about 750 ° C to about 800 ° C ( firing), a front electrode portion 140 having a plurality of front electrodes 141 and a plurality of front busbars 142, a conductive layer 155 for a rear electrode having a plurality of rear electrodes 151, and a plurality of The solar cell 11 is completed by forming the rear electrode 150 having the rear bus bar 152 and the plurality of rear electric field 172 (FIGS. 1 and 2).

That is, when the heat treatment is performed, the anti-reflection portion 130 of the contact portion is penetrated by the front electrode portion pattern 40 by lead (Pb) or the like contained in the front electrode portion pattern 40, thereby preventing the front electrode portion pattern ( 40 is in contact with the emitter portion 121, the front electrode portion 140 consisting of a plurality of front electrode 141 and the front bus bar 142 is formed. At this time, the front electrode pattern portion 41 of the front electrode portion pattern 40 becomes a plurality of front electrodes 141, and the front bus bar pattern portion 42 becomes a plurality of front bus bars 142.

In addition, the portion 153 in which the conductive layer pattern 55 for the rear electrode, the lower portion of the protective part 190 and the substrate 110 are mixed with each other is in contact with the substrate 110 to be a plurality of rear electrodes 151. The conductive layer 155 for the rear electrode including the plurality of rear electrodes 151 is completed, and the plurality of rear bus bar patterns 52 are also connected to the adjacent conductive layers 155 for the rear electrode to connect the plurality of rear bus bars. 152 is formed. As such, when the plurality of rear electrodes 151 are formed by using a laser beam, each rear electrode 151 may not only have components of the conductive layer 155 for the rear electrodes, but also components of the protection unit 190 and the substrate 110. It may be contained.

  Furthermore, during the heat treatment, the chemical bonding between the metal components contained in the patterns 40, 55, and 52 and the layers 121, 110, and 190 in contact with each other is performed, such that the front electrode portion 140 and the emitter portion 121 are formed. ), The contact resistance between the plurality of rear electrodes 151 and the substrate 110 and between the conductive layer 155 for the rear electrode and the rear busbar 152 is reduced, thereby improving the charge flow therebetween.

 In addition, in the heat treatment process, aluminum (Al), which is a content of the rear electrode 151, is diffused toward the substrate 110 in contact with the rear electrode 151, so that the substrate 110 is in contact with the rear electrode 151. A plurality of backside electric fields 172, which are portions doped with the same impurities as the dopant at a higher concentration than the substrate 110, are formed.

As described above, instead of forming the plurality of rear electrodes 151 using the laser beam, the rear electrodes of the substrate 110 are exposed by removing a portion of the protection unit 190 to expose the plurality of rear electrodes. 151 may be formed.

That is, as shown in FIGS. 3A to 3E, after the emitter portion 121, the antireflection portion 130, and the protection portion 190 are formed on the substrate 110, a portion of the protection portion 190 is removed. A plurality of exposed portions exposing a portion of the substrate 110 is formed. In this case, the exposed part of the protection unit 190 may be formed using a dry etching method, a wet etching method or a laser beam, and each exposed part has a stripe shape according to the shape of each back electrode 151 or in a predetermined direction. It may have a circular, elliptical, or polygonal shape that is disposed.

Next, using the screen printing method, the front electrode pattern 40 is formed on the anti-reflection portion 130, and the conductive layer pattern 55 for the rear electrode is formed on the protection portion 190 and the exposed substrate 110. In addition, the rear bus bar pattern 52 is formed on the protection unit 190 in contact with the conductive layer pattern 55 for the rear electrode.

Then, as described above, by heat-treating the substrate 110 having the patterns 40, 55, 52, the plurality of front electrode portions 140 and the protection portion 190 connected to the emitter portion 121 A rear electrode conductive layer 155 having a plurality of rear electrodes 151 connected to the substrate 110 through an exposed part, a plurality of rear bus bars 152 connected to the rear electrode conductive layer 155, and a plurality of rear electrode conductive layers 155. A plurality of rear electric field parts 172 are formed on the substrate 110 that is in contact with the rear electrode 151 of FIG. In this case, since the protection unit 190 is removed to form the plurality of rear electrodes 151 at the portion where the substrate 110 is exposed, each rear electrode 151 contains only a component of the conductive layer 155 for the rear electrode. can do.

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.

Claims (17)

Forming an emitter portion of a second conductivity type opposite to the first conductivity type on a first surface of the substrate having a first conductivity type,
Exposing a second surface of the substrate opposite to the first surface of the substrate to plasma to passivate the second surface using the plasma;
Forming a protection on said second surface of said passivated substrate, and
Forming a first electrode connected to the emitter part and a second electrode selectively connected to the substrate through the protection part;
Method for manufacturing a solar cell comprising a. In claim 1,
The passivation step is a method of manufacturing a solar cell using the ammonia (NH ₃ ) or nitrous oxide (N ₂ O) to generate the plasma. The method of claim 1 or 2,
The passivation step is a solar cell manufacturing method of producing the plasma using a direct PECVD method. 4. The method of claim 3,
The passivation step is a solar cell manufacturing method of generating the plasma using a frequency of 13.56MHz or 15MHz. In claim 1,
The protective part manufacturing method of a solar cell having a thickness of 100nm to 200nm. The method of claim 1 or 5,
The forming of the protective part may include forming the protective part using silicon oxide (SiOx), silicon nitride (SiNx), silicon oxynitride (SiNxOy), or aluminum oxide (Al ₂ O ₃ ). The method of claim 1 or 5,
If the first conductivity type is p-type, forming the protective portion is a method of manufacturing a solar cell to form the protective portion of aluminum oxide (Al ₂ O ₃ ). The method of claim 1 or 5,
If the first conductivity type is n-type, the forming of the protection portion is a solar cell manufacturing method of forming the protection portion of silicon nitride (SiNx) or silicon oxynitride (SiNxOy). The method of claim 1 or 5,
The protecting part forming step of forming a protective part of silicon oxide (SiOx) manufacturing method of a solar cell. In claim 1,
And forming an anti-reflection portion on the emitter portion. 11. The method of claim 10,
The forming of the anti-reflection portion may include forming the anti-reflection portion with silicon nitride (SiNx). The method of claim 10 or 11,
The anti-reflection portion of the solar cell manufacturing method having a refractive index of 2.0 to 2.1. 11. The method of claim 10,
The first electrode and the second electrode forming step,
Forming a first electrode pattern on the anti-reflection portion;
Forming a second electrode pattern on the protection part;
Selectively irradiating a laser beam to the second electrode pattern, and
Heat-treating the substrate having the first electrode pattern and the second electrode pattern
Including,
During the heat treatment step, the first electrode pattern penetrates the anti-reflective part to contact the emitter part to form the first electrode, and the second electrode pattern of the portion to which the laser beam is irradiated passes through the protection part. Selectively contacting a substrate to form the second electrode
Method for manufacturing a solar cell. 11. The method of claim 10,
The first electrode and the second electrode forming step,
Forming a first electrode pattern on the anti-reflection portion;
Selectively removing the protective part to selectively expose the second surface of the substrate,
Forming a second electrode pattern on the protection portion and on the exposed second surface of the substrate, and
Heat-treating the substrate having the first electrode pattern and the second electrode pattern
Including,
In the heat treatment step, the first electrode pattern penetrates the anti-reflection portion to contact the emitter portion to form the first electrode, and the second electrode pattern selectively contacts the two surfaces of the exposed substrate to form the first electrode. To form two electrodes
Method for manufacturing a solar cell. The method of claim 13 or 14,
In the forming of the first electrode pattern, a first paste is coated on the emitter part by screen printing and then dried to form the first electrode pattern. The forming of the second electrode pattern is a second paste different from the first paste. Method of manufacturing a solar cell is coated with a screen printing method and dried to form the second electrode pattern. 16. The method of claim 15,
The first paste contains silver (Ag), and the second face contains aluminum (Al). A substrate of a first conductivity type,
An emitter portion disposed on a first surface of the substrate and having a second conductivity type opposite to the first conductivity type,
A first electrode electrically connected to the emitter unit,
A passivation process using a plasma and positioned on a second surface of the substrate located opposite to the first surface of the substrate,
A first electrode connected to the emitter unit, and
A second electrode selectively connected to the substrate through the protection part
Solar cell comprising a.

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