KR101597825B1 - Solar Cell Method for solar cell and Heat Treatment Apparatus for Thermal Diffusion - Google Patents

Solar Cell Method for solar cell and Heat Treatment Apparatus for Thermal Diffusion Download PDF

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KR101597825B1
KR101597825B1 KR1020090067675A KR20090067675A KR101597825B1 KR 101597825 B1 KR101597825 B1 KR 101597825B1 KR 1020090067675 A KR1020090067675 A KR 1020090067675A KR 20090067675 A KR20090067675 A KR 20090067675A KR 101597825 B1 KR101597825 B1 KR 101597825B1
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substrate
emitter
source layer
impurity
doping source
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KR1020090067675A
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KR20110010224A (en
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심승환
정일형
김진아
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엘지전자 주식회사
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    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy

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Abstract

The present invention relates to a solar cell, a method of manufacturing a solar cell, and a thermal processing apparatus for thermal diffusion of a solar cell, wherein a method for manufacturing a solar cell according to an embodiment of the present invention includes: And a step of heating the source layer differentially to form a selective emitter structure all at once. In the solar cell according to the embodiment of the present invention, the impurity concentration of the surface of the first emitter portion and the second emitter portion is the same, The heat treatment apparatus for thermal diffusion of a solar cell according to an embodiment of the present invention has a structure in which the second pattern heating portion protrudes more than the first pattern heating portion.

Solar cell, selective emitter, heat treatment apparatus for thermal diffusion, temperature gradient, doping source layer

Description

TECHNICAL FIELD [0001] The present invention relates to a solar cell, a manufacturing method of the solar cell, and a heat treatment apparatus for thermal diffusion,

The present invention relates to a solar cell, a method of manufacturing a solar cell, and a heat treatment apparatus for thermal diffusion.

Typical solar cells have a substrate and an emitter layer made of different conductivity type semiconductors, such as p-type and n-type, and electrodes formed on the substrate and emitter, respectively. At this time, a p-n junction is formed at the interface between the substrate and the emitter.

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 by the photovoltaic effect, And the p-type semiconductor, for example, toward the emitter portion and the substrate, and are collected by electrodes electrically connected to the substrate and the emitter portion, respectively, and these electrodes are connected by electric wires to obtain electric power.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to simplify a manufacturing process of a solar cell having a selective emitter structure to reduce manufacturing process time and manufacturing cost.

A method of manufacturing a solar cell according to an embodiment of the present invention includes a step of forming a selective emitter structure at one time by differentially heating a doping source layer deposited on a substrate using a heat treatment apparatus for thermal diffusion of a solar cell, The solar cell according to the embodiment of the present invention has the same impurity concentration on the surfaces of the first emitter portion and the second emitter portion. In the heat treatment apparatus for thermal diffusion of the solar cell according to the embodiment of the present invention, It has a more protruding structure than the part.

According to the features of the present invention, the first and second emitter portions having different concentrations can be simultaneously formed by differentially heating the doping source layer deposited on the substrate by adjusting the temperature gradient of the heat treatment apparatus for thermal diffusion of the solar cell.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out 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, the thickness is enlarged to clearly represent the layers and regions. Like parts are designated with like reference numerals throughout the specification. It will be understood that when an element such as a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the element directly over another element, Conversely, when a part is "directly over" another part, it means that there is no other part in the middle.

A solar cell according to an embodiment of the present invention will be described with reference to FIGS. 1 and 7. FIG.

FIG. 1 is a partial perspective view of a solar cell according to an embodiment of the present invention, and FIG. 7 is a cross-sectional view of the solar cell of FIG. 1 cut along the line I-I.

1 and 7, a solar cell 1 according to the present embodiment includes a substrate 101, an emitter layer 102 located on one side of the substrate 101, A plurality of first electrodes (hereinafter, referred to as "front electrodes") 105 electrically connected to the emitter layer 102, an anti-reflection layer 104 positioned on the other surface of the substrate 101 A second electrode (hereinafter referred to as a "rear electrode") 106 electrically connected to the substrate 101 and a rear electric field 107 disposed between the substrate 101 and the rear electrode 106.

The substrate 101 is a semiconductor substrate made of silicon of the first conductivity type, for example, p-type conductivity type. Here, the silicon may be a single crystal silicon, a polycrystalline silicon substrate, or an amorphous silicon. When the substrate 101 has a p-type conductivity type, it contains an impurity of a trivalent element such as boron (B), gallium, indium or the like. Alternatively, however, the substrate 101 may be of the n-type conductivity type and may be made of a semiconductor material other than silicon. When the substrate 101 has an n-type conductivity type, the substrate 101 may contain impurities of pentavalent elements such as phosphorus (P), arsenic (As), antimony (Sb)

The emitter layer 102 is an impurity portion having a second conductive type, for example, an n-type conductive type, which is opposite to the conductive type of the substrate 101. The emitter layer 102 is a light receiving surface of the substrate 101 Respectively.

The emitter layer 102 has a first emitter portion 102a and a second emitter portion 102b having different impurity concentrations. In this embodiment, the impurity concentration of the second emitter section 102b is higher than the impurity concentration of the first emitter section 102a. The depth of impurity doping of the second emitter section 102b is larger than the depth of doping of the first emitter section 102a and the thickness of the second emitter section 102b is larger than the thickness of the first emitter section 102a. Since the impurity concentration and the doping depth of the second emitter section 102b are larger than that of the first emitter section 102a, the sheet resistance of the second emitter section 102b is smaller than the sheet resistance of the first emitter section 102a. This emitter layer 102 forms a p-n junction with the substrate 101.

In the selective emitter structure according to the embodiment of the present invention, the doping depths of the first emitter portion and the second emitter portion are different from each other, but unlike the conventional process, the concentrations of the surfaces of the first and second emitter portions are uniform .

The concentration of the impurity contained in the doped source layer applied on the substrate is constant, and the temperature gradient of the thermal annealing apparatus for thermal diffusion is selectively changed, as compared with the process of forming the selective emitter structure using the mask. The impurity concentration of the substrate surface formed with the first and second emitter portions is uniform.

Thermal diffusion also proceeds in the horizontal direction because the particles are moving in a region having a high particle density and a region having a low particle density. Since the first and second emitter portions are simultaneously formed in the present invention, diffusion in the horizontal direction is less likely to occur as compared with the step of forming a selective emitter structure using a mask, so that the first emitter portion and the second emitter portion The distinction is clear.

On the other hand, in the step of forming the selective emitter structure using the etching process, since at least one of the first and second emitters is etched, the surface of the first emitter portion and the surface of the second emitter portion are the same The surface of the first emitter portion and the surface of the second emitter portion are located on the same plane because the etching process is not used in the present invention.

Due to the built-in potential difference due to the pn junction, the electron-hole pairs, which are charges generated by the light incident on the semiconductor substrate 101, are separated into electrons and holes, And the holes move toward the p-type. Therefore, when the substrate 101 is p-type and the emitter layer 102 is n-type, the separated holes move toward the substrate 101 and the separated electrons move toward the emitter layer 102, Becomes a majority carrier, and the electrons in the emitter layer 102 become a majority carrier.

Since the emitter layer 102 forms a pn junction with the substrate 101, the emitter layer 102 has a p-type conductivity type when the substrate 101 has an n-type conductivity type unlike the present embodiment . In this case, the separated electrons move toward the substrate 101 and the separated holes move toward the emitter layer 102.

When the emitter layer 102 has an n-type conductivity type, the emitter layer 102 is doped with a dopant of a pentavalent element such as phosphorus (P), arsenic (As), antimony (Sb) Doped impurity such as boron (B), gallium, indium or the like may be doped to the substrate 101 when the substrate 101 has a p-type conductivity type.

An antireflection film 104 made of a silicon nitride film (SiNx) or a silicon oxide film (SiO 2) is formed on the emitter layer 102. The antireflection film 104 reduces the reflectivity of incident sunlight and increases the selectivity of a specific wavelength region, thereby increasing the efficiency of the solar cell. The antireflection film 104 may have a thickness of approximately 70 nm to 80 nm. The antireflection film 104 may be omitted if necessary.

The plurality of front electrodes 105 extend in one direction at a predetermined interval on the second emitter section 102b of the emitter layer 102 and are electrically connected to the second emitter section 102b. And a plurality of bus electrodes 105b extending in a direction crossing the finger electrodes 105a and connected to the finger electrodes 105a.

The plurality of finger electrodes 105a collect electrons, for example, electrons moving toward the emitter unit 102 and move them to a desired place, and the plurality of bus electrodes 105b move along the finger electrodes 105a connected thereto Collects electrons and outputs them to the outside.

Therefore, in order to increase the collecting efficiency of moving electrons, the width of each bus electrode 305b is larger than the width of each finger electrode 105a.

As described above, the second emitter section 102b functions as an ohmic contact which contacts the front electrode 105 positioned thereon and lowers the contact resistance with the front electrode 105. [

The front electrode 105 is made of at least one conductive metal material such as Ni, Cu, Ag, Al, Sn, Zr, Zn), indium (In), titanium (Ti), gold (Au), and combinations thereof, but may be made of other conductive metal materials.

The back electrode 106 is formed on the entire rear surface of the substrate 101 facing the incident surface and collects an electric charge, for example, a hole, which is electrically connected to the substrate 101 and moves toward the substrate 101 .

The back electrode 106 is made of a conductive metal material. Examples of the conductive metal material include nickel (Ni), copper (Cu), silver (Ag), aluminum (Al), tin (Sn) May be at least one selected from the group consisting of indium (In), titanium (Ti), gold (Au), and combinations thereof, but may be made of other conductive metal materials.

A rear electric field portion 107 is positioned between the rear electrode 106 and the substrate 101. The rear electric field portion 107 is a region in which impurities of the same conductivity type as that of the substrate 101 are doped heavily than the substrate 101, for example, a p + region. (For example, electrons) to the rear side of the substrate 301 due to the potential barrier generated due to the difference in impurity concentration between the substrate 101 and the rear electric section 107, The electrons and holes are prevented from recombining and disappearing.

The operation of the solar cell 1 having such a structure is as follows.

When light is irradiated to the solar cell 1 and enters the semiconductor substrate 101 through the antireflection film 104 and the emitter layer 102, electron-hole pairs are generated in the semiconductor substrate 101 by light energy. At this time, the reflection loss of the light incident on the substrate 101 is reduced by the anti-reflection film 104, and the amount of light incident on the substrate 101 is increased.

These electron-hole pairs are separated from each other by the pn junction of the substrate 101 and the emitter layer 102 so that the electrons move to the emitter layer 102 having the n-type conductivity type and the holes become the p- To the substrate 101 having the light-emitting layer. Electrons migrating toward the emitter layer 102 are collected by the finger electrode 105a of the front electrode 105 contacting the second emitter section 102b and then transferred to be collected by the bus electrode 106b, And the holes moved toward the light emitting element 101 are collected by the rear electrode 106. When the bus electrode 105b and the rear electrode 106 are connected to each other by a conductor, a current flows and the external power is used.

At this time, since the front electrode 105 directly contacts the second emitter layer 102b doped with the impurity at a high concentration, the contact force with the emitter layer 102 is improved. As a result, the electron transfer efficiency is improved, The efficiency of the device increases.

Next, a method of manufacturing a solar cell according to the first and second embodiments of the present invention will be described with reference to FIGS. 2 to 6. FIG.

3 is a cross-sectional view illustrating a method of manufacturing a selective emitter layer of a solar cell according to a first embodiment of the present invention, and FIG. 4 is a cross-sectional view illustrating a method of manufacturing a selective emitter layer of a solar cell according to a second embodiment of the present invention . FIGS. 2, 5, and 6 are cross-sectional views illustrating a common method of manufacturing solar cells according to the first and second embodiments of the present invention.

As shown in FIG. 2, a method of manufacturing a solar cell according to the first and second embodiments of the present invention includes the steps of forming a first conductive type first impurity on a substrate 101 doped with a first conductive type A doping source layer 110 containing a second impurity of the second conductivity type in the substrate 101 is pre-deposited.

The conductive type of the substrate 101 may be p-type or n-type. However, when the substrate 301 has a p-type conductivity type, the lifetime and the mobility of the minority carriers are large and can be preferably used. The p-type substrate 101 is doped with a group III element such as B, Ga, or In. At this time, the substrate 101 may be a substrate on which a damaged portion generated on the surface of the substrate 101 is removed through a wet etching method or the like during the slicing process of silicon.

When the substrate 101 is a p-type, the doping source layer 110 has an n-type conductivity type, and a Group 5 element such as P, As, or Sb is doped with an impurity.

The doping source layer 110 may be formed by, for example, placing the substrate 101 in a furnace, injecting an oxygen gas and an impurity gas of a second conductivity type to form an impurity of the second conductivity type on the substrate 101 And is formed by pre-deposition. At this time, oxygen and impurity gas react with each other on the substrate 101 to form a doping source layer 110, which is an oxide containing an impurity. Here, when the substrate 101 is p-type, the dopant gas may be used are POCl 3, In this case, the doped source layer 110 may be an oxide (phosphorus silicate glass, PSG) containing phosphorus, such as P 2 O 5 is .

Alternatively, the doping source layer 110 can be formed by using a spraying method or a screen printing method using a paste or the like as an alternative example. In this case, if an impurity source containing an impurity of the second conductivity type is coated on the substrate 101 using a spraying method or a doping paste is printed and deposited on the substrate 101, A doping source layer 110 is formed. At this time, it is preferable that the doping source layer 110 is entirely deposited on the upper surface of the substrate to simultaneously form the first and second emitter portions (not shown).

3 is a cross-sectional view illustrating a process of forming a selective emitter portion of a solar cell according to a first embodiment of the present invention.

The doping source layer 110 is formed on the substrate 101 according to the process described in FIG. 2 and then a thermal processing apparatus 201 for thermal diffusion is disposed on the doping source layer 110, as shown in FIG. 3, The first emitter layer 102a and the second emitter layer 102b having different concentrations from each other are differentially heated by differentially heating the source layer 110 to drive-in diffuse impurities of the second conductivity type into the substrate 101, And the tab portion 102b can be formed at the same time. As described above, the selective emitter structure having the first emitter portion and the second emitter portion can be simultaneously formed by one process, thereby shortening the manufacturing process of the solar cell.

As shown in FIG. 3, the thermal processing apparatus 201 for thermal diffusion includes a first pattern heating section 201a and a second pattern heating section 201b on the same plane. Although not shown, the apparatus may further include a current application unit for applying a current to the first and second pattern heating units 201a and 201b.

The heating material of the heat treatment apparatus for thermal diffusion 201 may be silicon carbide (SiC), carbon, tungsten, or the like, which is applicable even at a temperature of 1000 degrees or higher.

The second pattern heating unit 201b of the heat treatment apparatus 201 for thermal diffusion has a structure more protruded than the first pattern heating unit 201a. The projecting shape of the second pattern heating portion 201b corresponds to the pattern of the front electrode 105 to be placed on the substrate 101. [

That is, the heat treatment apparatus 201 for thermal diffusion may include a first pattern heating unit 201a and a second pattern heating unit 201a having a structure more protruded than the first pattern heating unit 201a according to the wiring position of the front electrode 201b.

At this time, it is preferable that the second pattern heating part 201b is close to a part of the doping source layer 110 deposited corresponding to the formation position of the front electrode, It may be in contact with the source layer 110. This is because the thermal conductivity of the thermal processing apparatus 201 for thermal diffusion is higher than that of the substrate 101 so that even if the second pattern heating unit 201b contacts the doping source layer 110, So that an applied current flows.

In general, the temperature of the thermal processing apparatus 201 for thermal diffusion to selectively heat the doping source layer 110 is suitably 800 to 900 degrees. In order to control the temperature of the thermal processing apparatus 201 for thermal diffusion, the temperature of the thermal processing apparatus 201 for thermal diffusion can be controlled by adjusting the heat generation temperature and the heat generation time.

In addition, the temperature gradient can be controlled by the structural characteristics of the heat treatment apparatus 201 for thermal diffusion having the structure in which the second pattern heating unit 201b protrudes more than the first pattern heating unit 201a.

That is, since the distance h1 between the second pattern heating portion 201b and the doping source layer 110 is closer to the distance h2 between the first pattern heating portion 201a and the doping source layer 110, The doping source layer region deposited at the position to be wired is selectively heated to a higher temperature than the other doping source layer regions.

The second pattern heating unit 201b heats the doping source layer region deposited at the position where the front electrode which is a part of the surface of the substrate is to be wired to the second temperature and the first pattern heating unit 201a heats the doping source layer region, The region can be heated to a first temperature higher than the second temperature.

Further, by injecting an inert cooling gas such as nitrogen (N 2 ) and argon (Ar) gas between the substrate and the space of the heat treatment apparatus for thermal diffusion, the temperature gradient of the thermal processing apparatus 201 for thermal diffusion is supplemented Can be adjusted.

Therefore, the second conductive type impurities are diffused in the substrate differentially by the differential heating due to the difference in distance from the substrate of the thermal diffusion thermal processing apparatus and cooling by the cooling gas, so that the first emitter The second emitter section 102a and the second emitter section 102b may be formed at the same time.

That is, the second pattern heating portion 201b that heats a portion of the doping source layer deposited at the position where the front electrode is to be wired to the second temperature of the high temperature, the second emitter portion 102b is positioned at a position The second emitter section 102b has a higher impurity concentration and a higher diffusion depth than the first emitter section 102a.

The distance between the surface of the substrate 101 facing each other and the surface of the heat treatment apparatus 201 for heat diffusion is constant so that the diffusion effect according to the heat applied to the doping source layer can be uniform. In addition, it is preferable that the wiring width tb of the second pattern heating portion 201b is equal to or smaller than the front electrode width wb.

4 is a cross-sectional view illustrating a process of forming a selective emitter portion of a solar cell according to a second embodiment of the present invention.

A doping source layer 110 is formed on the substrate 101 according to the process described in Figure 2 and then a temperature gradient is applied to the top of the doping source layer 110 in a manner different from Figure 3, The doping source layer 110 is heated differentially by placing the thermal diffusion apparatus 301 for adjusting the concentration of impurities of the second conductivity type in the substrate to diffuse the impurities of the second conductivity type in the substrate, The emitter section 102a and the second emitter section 102b can be formed at the same time.

In this case, the pattern of the thermal diffusion apparatus 301 according to the second embodiment of FIG. 4 depends on the pattern of the front electrode 105 to be placed on the substrate 101, as in the first embodiment of FIG. However, the thermal diffusion apparatus 301 according to the second embodiment of FIG. 4 has a low resistance portion 301a and a high resistance portion 301b in consideration of the wiring position of the front electrode, .

3, silicon carbide (SiC), carbon (Carbon), or tungsten (Tungsten) can be applied to the heat generating material of the thermal diffusion apparatus 201 even at a temperature of 1000 degrees or higher.

The division according to the low-resistance portion 301a and the high-resistance portion 301b of the thermal diffusion thermal processing apparatus 301 is in accordance with the Joule's law. The law of juxtaposition is the law of juxtaposition that occurs when a current flows in a conductor. That is, the heat quantity Q generated by the current is proportional to the square of the current intensity I, R of the conductor, and time t through the current. The amount of heat generated when the current flows for t seconds can be expressed as Q = 0.24 I 2 Rt.

The R of the conductor is proportional to the length L of the conductor and is inversely proportional to the area S of the conductor when the current flowing through the thermal diffusion apparatus 301 is constant for a predetermined period of time. the electric resistance of the thermal diffusion thermal processing apparatus 301 can be adjusted by adjusting the electric resistance of the thermal diffusion processing apparatus 301.

Therefore, when the wiring width tb of the high resistance of the thermal diffusion thermal processing apparatus 301 is fixed so as to be equal to or smaller than the front electrode width Wb, the thickness ta of the thermal diffusion thermal processing apparatus 301 can be controlled, The gradient can be adjusted.

In other words, as the thickness ta of the thermal diffusion apparatus 301 is increased, the temperature difference between the low-resistance section 301a and the high-resistance section 301b becomes relatively large.

In this case, when the high-resistance portion 301b of the thermal diffusion processing apparatus 301 heats the doping source layer 110 deposited at the formation position of the front electrode to a different high temperature, Is selectively heated to a higher temperature than other doping source layer regions.

The temperature gradient of the thermal processing apparatus 301 for thermal diffusion by injecting an inert cooling gas such as nitrogen (N 2 ) and argon (Ar) gas between the substrate and the space of the heat treatment apparatus for thermal diffusion 301 As shown in FIG.

Therefore, the second conductive type impurities are diffused in the substrate by the differential heating according to the difference in resistance of the thermal diffusion heat treatment apparatus and the cooling by the cooling gas, so that the first emitter section 102a And the second emitter portion 102b may be formed at the same time.

That is, the second emitter portion 102b is formed in the substrate below the doping source layer region deposited at the position where the front electrode is to be wired, and the second emitter portion 102b is formed in the first emitter portion 102a ) And a deep diffusion depth.

The wiring width tb of the high resistance portion 301b of the thermal diffusion thermal processing apparatus 301 is preferably equal to or smaller than the width Wb of the front electrode.

Although not shown in the drawing, a selective emitter portion may be formed by mixing the first embodiment shown in FIG. 3 and the second embodiment shown in FIG.

Specifically, by simultaneously controlling the distance between the thermal diffusion apparatus and the doping source layer 110 and the thickness ta of the thermal diffusion apparatus, the doping source layer 110 is heated differentially to form the second The first emitter section 102a and the second emitter section 102b having different concentrations from each other can be formed at the same time by implanting and diffusing conductive type impurities.

After forming the first and second emitter portions according to the first embodiment according to FIG. 3 and the second embodiment according to FIG. 4, a doping source layer deposited on the substrate 101 as shown in FIG. 5 Remove. At this time, the doping source layer can be removed in various ways such as a wet visual process using hydrofluoric acid.

Although not shown, after removing the first emitter portion 102a formed on the side surface and the rear surface except for the first emitter portion 102a formed on the front surface of the substrate 101 by performing an edge isolation process, The antireflection film 104 is formed on the surface of the substrate including the first and second emitter portions 102. [

Finally, as shown in FIG. 7, the front electrode paste is printed on the antireflection film 104 by screen printing to form a pattern for the finger electrode and a pattern for the bus electrode crossing the pattern for the finger electrode. Are simultaneously formed. The front electrode paste includes silver (Ag) and glass frit. On the rear surface of the substrate 101, a rear electrode paste containing aluminum (Al) is printed to form a rear electrode pattern. At this time, the printing order of the pattern for the front electrode and the pattern for the rear electrode can be changed.

A plurality of front electrodes 105, that is, finger electrodes 105a, which are electrically connected to the second emitter section 102b by performing a heat treatment process on the substrate 101 on which the pattern for the front electrode and the pattern for the rear electrode are formed, A bus electrode 105b, a back electrode 106 electrically connected to the substrate 101, and a rear electrode 107 to complete the solar cell 1 (FIG. 1).

That is, by the heat treatment process, the front electrode pattern passes through the antireflection film 104 and is electrically connected to the second emitter section 102b. Further, by the heat treatment process, the aluminum (Al) is doped into the substrate 101 to form the rear electric section 107 having an impurity concentration higher than that of the substrate 101. [ As described above, aluminum (Al) is a Group 3 element, and the rear electric section 107 has a P + conductive type, thereby preventing recombination of electrons and holes and allowing the holes to move easily toward the rear electrode 106.

At this time, the front electrode 105 includes silver (Ag) and has good electrical conductivity. Since the back electrode 106 includes aluminum (Al) having good affinity with silicon, not only good electrical conductivity, 101). ≪ / RTI >

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 embodiments, but, on the contrary, It will be understood that the invention may be varied and changed without departing from the scope of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a partial perspective view of a solar cell according to an embodiment of the present invention, and FIG. 7 is a cross-sectional view of the solar cell of FIG. 1 cut along the line I-I.

FIG. 3 is a cross-sectional view illustrating a process of forming a selective emitter portion of a solar cell according to a first exemplary embodiment of the present invention, FIG. 4 is a cross-sectional view illustrating a process of forming a selective emitter portion of a solar cell according to a second exemplary embodiment of the present invention Fig.

FIGS. 2, 5, and 6 are cross-sectional views illustrating a common method of manufacturing solar cells according to the first and second embodiments of the present invention. That is, FIG. 2 is a cross-sectional view showing a process in which a doping source layer is formed on a substrate, FIG. 5 is a view showing a process of removing a doping source layer deposited on a substrate, Fig.

Description of the Related Art

Solar cell (1); A substrate 101;

The emitter layer 102 - the first emitter section 102a, the second emitter section 102b;

An antireflection film 104, a front electrode 105, a rear electrode 106, a rear electric part 107;

A doping source layer 110;

A thermal processing apparatus 201 for thermal diffusion according to the second embodiment, a first pattern heating unit 201a, a second pattern heating unit 201b,

The thermal processing apparatus 301 for thermal diffusion according to the second embodiment includes a low resistance portion 301a, a high resistance portion 301b,

Claims (31)

Depositing a doping source layer comprising a second impurity of a second conductivity type opposite to the first conductivity type on a substrate doped with a first impurity of a first conductivity type; The doping source layer deposited on the substrate is heated to different temperatures to form a Forming a first emitter portion and a second emitter portion having different concentrations, Forming an anti-reflection film on a surface of the substrate having the first and second emitter portions, Forming a front electrode electrically connected to the second emitter portion; And forming a back electrode electrically connected to the substrate, In forming the first and second emitter portions, And a second pattern heating part having a first pattern heating part and a second pattern heating part protruding more than the first pattern heating part is used to adjust the distance between the second pattern heating part and the doping source layer to the first pattern heating part, Heating a part of the surface of the substrate to a second temperature using the second pattern heating unit while being positioned closer to the substrate than the distance between the pattern heating unit and the doping source, To a first temperature lower than the second temperature. delete The method according to claim 1, And a cooling gas is injected between the substrate and the space of the heat treatment apparatus for thermal diffusion. The method according to claim 1, Wherein the first and second pattern heating units are formed on a plate, and the second heating unit is more protruded than the first heating unit. delete delete delete The method according to claim 1, And the pattern of the second pattern heating portion corresponds to the pattern of the front electrode. The method according to claim 1, Wherein a wiring width of the second pattern heating portion is equal to or smaller than a width of the front electrode. Depositing a doping source layer comprising a second impurity of a second conductivity type opposite to the first conductivity type on a substrate doped with a first impurity of a first conductivity type; Forming a first emitter portion and a second emitter portion having different concentrations on the substrate by heating the doping source layer deposited on the substrate to different temperatures; Forming an anti-reflection film on a surface of the substrate having the first and second emitter portions, Forming a front electrode electrically connected to the second emitter portion; And forming a back electrode electrically connected to the substrate, In forming the first and second emitter portions, Resistance portion and a high-resistance portion formed to a thickness smaller than the low-resistance portion, the distance between the high-resistance portion and the doping source layer is set to be closer to the distance between the low-resistance portion and the doping source And heating a portion of the surface of the substrate to a second temperature using the high resistance portion and heating the remaining region of the surface of the substrate to a first temperature lower than the second temperature using the low resistance portion Gt; 11. The method of claim 10, And a cooling gas is injected between the substrate and the space of the heat treatment apparatus for thermal diffusion. delete 11. The method according to claim 1 or 10, Wherein depositing the doping source layer comprises: Impurity of the second conductivity type included in the impurity gas injected into the furnace is deposited on the substrate. 14. The method of claim 13, Wherein the impurity gas is POCl 3 . The method according to claim 1 or 10, Wherein depositing the doping source layer comprises: Wherein a doping paste containing impurities of the second conductivity type is printed on the substrate to deposit the doping paste. The method according to claim 1 or 10, Wherein depositing the doping source layer comprises: Wherein an impurity source containing an impurity of the second conductivity type is coated on the substrate by a spray method to deposit the impurity source. 11. The method according to claim 1 or 10, Wherein depositing the doping source layer comprises: A method of manufacturing a solar cell in which the doping source layer is entirely deposited on the substrate The method according to claim 1 or 10, Wherein the doping source layer is phosphorus silicate glass (PSG). 11. The method according to claim 1 or 10, In forming the first and second emitter portions, Wherein the first emitter portion and the second emitter portion are simultaneously formed. The method according to claim 1 or 10, In forming the first and second emitter portions, And the second emitter portion is formed under the front electrode. The method according to claim 1 or 10, And removing the doping source layer deposited on the substrate after forming the first and second emitter portions. The method according to claim 1 or 10, And the second emitter portion has a smaller sheet resistance than the first emitter portion. The method according to claim 1 or 10, And the impurity concentration of the second emitter portion is higher than the impurity concentration of the first emitter portion. The method according to claim 1 or 10, Wherein a depth of the impurity implantation in the second emitter portion is larger than a depth of impurity implantation in the first emitter portion. In a selective emitter structure having a first emitter portion and a second emitter portion having different sheet resistances, Depositing a doping source layer containing a second impurity of a second conductivity type in the same concentration as the first conductivity type opposite to the first conductivity type on the substrate doped with the first impurity of the first conductivity type, And a second pattern heating unit having a structure more protruded than the pattern heating unit, a distance between the second pattern heating unit and the doping source layer is set to a distance between the first pattern heating unit and the doping source A second pattern heating unit for heating a part of the surface of the substrate to a second temperature and for heating the remaining area of the substrate surface to a temperature higher than the second temperature by using the first pattern heating unit, And the surface concentration of the first emitter portion and that of the second emitter portion are the same. 26. The method of claim 25, Wherein the surface of the first emitter portion and the surface of the second emitter portion are located on the same plane. 26. The method of claim 25, Wherein the doping depths of the first emitter portion and the second emitter portion are different from each other. The first pattern heating section and the second pattern heating section are formed on a plate, Wherein the second pattern heating unit further protrudes from the first pattern heating unit. 29. The method of claim 28, Wherein the first pattern heating unit heats a part of the surface of the solar cell to a first temperature and the second pattern heating unit heats the remaining area to a second temperature different from the first temperature. 30. The method of claim 29, Wherein the second temperature is higher than the first temperature. 29. The method of claim 28, And a current application unit for applying a current to the first and second pattern heating units.
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