KR20100128153A - Laser ablation apparatus and method for manufacturing opening using it - Google Patents

Abstract

PURPOSE: A laser etching apparatus and an aperture forming method using the same are provided to form a gap pattern on a rear passivation layer through a further simplified process using the laser etching technology in stead of photo etching technology in the manufacturing process of thin solar battery of high efficiency. CONSTITUTION: A stage part(160) supports the silicon substrate of solar battery formed with the rear passivation layer. A laser generator(110) generates the laser beam adjusted according to the passivation information. A beam forming unit(130) modifies the size and the shape of a spot of the laser beam according to the size and the shape of the aperture. A projection unit(150) concentrates the laser beam scanned by the scanning unit and irradiates the laser beam.

Description

Laser ablation apparatus and method for manufacturing opening using it

The present invention relates to a solar cell, and more particularly, to a laser etching apparatus used for manufacturing a solar cell and a method of forming a void using the same.

A solar cell is a semiconductor device that converts light energy generated from the sun into electrical energy by a photovoltaic effect. Depending on the type of solar cell, it can be classified into silicon solar cell and compound semiconductor solar cell. Among these, silicon solar cells are classified into crystalline silicon solar cells such as monocrystalline or polycrystalline silicon solar cells and amorphous silicon solar cells.

Among these, crystalline silicon solar cells use a single crystal or polycrystalline silicon wafer produced by cutting a single crystal or polycrystalline silicon ingot as a base. Generally, a p-type silicon wafer is used as a solar cell substrate, and an n-type emitter, an anti-reflection coating (ARC), and a front contact are formed on the front surface of the solar cell substrate. A back electrode and a back surface field (BSF) are formed on the rear surface of the solar cell substrate.

Here, the backside electric field is a kind of high-low junction, which suppresses the migration of the minority electrons to the backside by an energy barrier having a field effect. This decreases the probability that electrons, which are minority carriers, exist in the rear side, thereby decreasing the probability of recombination with holes, thereby lowering the rear side recombination speed.

Trivalent aluminum as a metal constituting the back electrode diffuses into the tetravalent silicon constituting the substrate and forms a p-type semiconductor region. During firing, the back electrode of aluminum diffuses to the back surface of the silicon substrate and forms a back electric field.

In the conventional structure in which the solar cell substrate made of silicon and the back electrode made of metal are in direct contact to form a back electric field, many defects exist at the interface between silicon and metal as the solar cell substrate and the back electrode make direct contact at the back. . This defect becomes a place where electrons and holes recombine and disappear. This back structure has a low back reflectance of less than 65% and a high back recombination rate of 750 cm / s.

1 is a cross-sectional view of a solar cell having a thick silicon substrate, and FIG. 2 is a cross-sectional view of a solar cell having a thin silicon substrate. Here, reference numeral 2 denotes a back metal electrode.

Referring to FIG. 1, when the silicon substrate 1 is sufficiently thick, incident light can be sufficiently absorbed inside the silicon substrate 1. In this case, since less light reaches the rear surface, less charge is generated from the rear surface, thereby reducing the amount of photo-generated charge. In other words, since the photogenerated charge is less likely to be collected by both electrodes, it hardly contributes to efficiency.

Silicon wafer takes about 60% of the manufacturing cost of crystalline silicon solar cell, and as shown in FIG. 2, the thickness of silicon substrate 3 is made thin (in FIGS. 1 and 2, where T1> T2). By reducing the manufacturing cost can be reduced. However, in the case where the thickness of the silicon substrate 3 is reduced to seek thinning, the path capable of absorbing incident light, that is, the light absorption path, is shortened.

As the silicon substrate 3 becomes thinner, the recombination at the surface becomes more important as compared to the recombination of electrons and holes generated inside the silicon substrate 3, and therefore, the recombination rate at the surface needs to be lowered.

In the thick silicon substrate 1, the front recombination rate, which is the portion where light is incident, greatly influences the efficiency of the solar cell. However, in the thin silicon substrate 3, not only the front recombination rate but also the rear recombination rate contributes to the solar cell efficiency. It grows bigger.

In this case, when the passivation layer is formed on the rear surface, surface defects of the silicon substrate may be reduced, thereby lowering the recombination rate. In addition, the rear structure of the rear passivation serves as a rear reflection layer, and the light absorption path that is not absorbed inside the thin silicon substrate may be reflected back from the rear reflection layer into the silicon substrate to increase the light absorption path.

In this case, if the rear structure is the rear point contact structure, the rear reflection can be relatively increased and the rear recombination speed can be lowered. 3 is a cross-sectional view of a solar cell having such a back point contact structure. When the solar cell has a back point contact structure, as the light absorption path increases, the amount of charge generated by the photovoltaic cell increases, thereby increasing the short circuit current. In addition, it is possible to improve absorption characteristics for long wavelengths penetrating to the rear surface of the silicon substrate.

The passivation layer 5 is mainly composed of dielectric materials and thus is close to an insulator. Therefore, in order to collect charges generated in the silicon substrate, in particular holes, in the back electrode, voids need to be formed in the passivation layer 5. These pores are a path through which a current can pass through the silicon substrate and the back metal electrode directly contact.

The p-type semiconductor region is formed inside the silicon substrate by diffusion of aluminum from the back electrode formed of aluminum through the pores of the passivation layer to serve as a local back field (4). The local rear electric field 4 formed on the silicon substrate is heavily doped with aluminum so that the contact resistance is low, so that current can flow well through this portion.

In manufacturing a solar cell having a back point contact structure, a photolithography technique is used to form voids. In the case of using a photolithography technique, the photolithography technique is manufactured through a complex process of several steps, and the photolithography technique is expensive, complicated in process steps, long in manufacturing time, and high in manufacturing cost. In addition, photoresist used for photolithography may contaminate unwanted parts, and in chemical wet etching, toxic chemicals are used to generate wastewater, which causes environmental problems and wastewater treatment problems.

The background art described above is technical information possessed by the inventors for the derivation of the present invention or acquired during the derivation process of the present invention, and is not necessarily a publicly known technique disclosed to the general public before the application of the present invention.

The present invention provides a laser etching apparatus and a solar cell using the same, which can form a pore pattern on a rear passivation layer through a simplified process using a laser etching technique instead of a photolithography technique in the manufacture of a highly efficient thinned solar cell. It is to provide a manufacturing method.

Another object of the present invention is to provide a laser etching apparatus capable of forming a pore pattern having various sizes, intervals, and array shapes in a large area in a very short time using a galvano mirror, and a method of manufacturing a solar cell using the same.

In addition, the present invention is a laser etching apparatus capable of manufacturing a thin-film solar cell of high efficiency and eco-friendly yet does not require any consumables such as masks or pot resists, low maintenance costs, no waste water and no chemicals It is to provide a solar cell manufacturing method.

According to an aspect of the present invention, in the laser etching apparatus for forming a void in the back passivation layer during solar cell manufacturing, the stage portion for mounting the silicon substrate of the solar cell with the back passivation layer, and the back surface structure of the silicon substrate A laser oscillation unit for oscillating the laser beam adjusted according to the above, a beam forming unit for modifying the size and shape of the spot of the laser beam according to the size and shape of the voids, and the laser beams according to the air gap pattern in which one or more voids are arranged. There is provided a laser etching apparatus including a scanning unit for scanning to be irradiated at the position of the and a projection unit for condensing and irradiating the laser beam scanned by the scanning unit.

The back surface structure may be saw damage etching (SDE) structure.

Or the back surface structure may be a textured structure. Here, the laser oscillator may oscillate the laser beam finely adjusted according to one or more of the size and shape of the pyramid formed on the back surface of the silicon substrate.

According to another aspect of the invention, in the solar cell manufacturing method for forming a void by using a laser etching device, (a) preparing a silicon substrate having a passivation layer formed on the back, (b) for the passivation layer Analyzing the passivation layer information, (c) adjusting laser processing conditions of the laser etching apparatus according to the analyzed passivation layer information, and (d) forming a void pattern in the passivation layer using the laser etching apparatus. Provided is a method of forming a gap of a solar cell comprising a.

The back surface structure may be saw damage etching (SDE) structure.

Or the back surface structure may be a textured structure. Here, step (c) may finely adjust the laser processing conditions according to one or more of the size and shape of the pyramid formed on the back surface of the silicon substrate.

Other aspects, features, and advantages other than those described above will become apparent from the following drawings, claims, and detailed description of the invention.

According to a preferred embodiment of the present invention, a pore pattern may be formed on the rear passivation layer through a simplified process by using laser etching instead of photolithography in the process of manufacturing a highly efficient thinned solar cell.

In addition, by using a galvano mirror, it is possible to form a void pattern having various sizes, intervals and arrangement shapes in a large area in a very short time.

In addition, maintenance costs are low because no consumables such as masks or pot resists are required, and wastewater does not occur and chemicals are not used, thereby making it possible to manufacture an eco-friendly and highly efficient thinned solar cell.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

In the present invention, the pore pattern refers to a pattern in which at least one pore, which is an electrical connection path between the inside of the silicon substrate and the back electrode, is arranged on the back passivation layer of the silicon substrate of the solar cell. The size of the pore pattern can be represented by the ratio of the sum of the area of all the pores with respect to the back surface area of the silicon substrate, and each pore can be arranged at regular intervals or irregularly with regularity.

Hereinafter, a method of forming a pore pattern in a solar cell according to a conventional photolithography technique will be described in detail with reference to the accompanying drawings of an embodiment of the present invention.

4 is a flowchart illustrating a method of forming a pore pattern in a rear passivation layer of a solar cell according to a conventional photolithography technique.

First, the passivation layer 11 is formed on the back surface of the silicon substrate 10 of the solar cell (see (a)).

Then, the photoresist 12 is coated on the passivation layer 11, and a soft baking process is performed (see (b)). The photoresist 12 is a photo sensitive material and will be apparent to those of ordinary skill in the art.

In order to form a pore pattern in the passivation layer 11, a portion of the photoresist 12 corresponding to the pore pattern must be removed. To do this, the following process is performed.

An exposure process is performed for a predetermined time using the photomask 13 on which the photoresist pattern corresponding to the void pattern is formed (see (c)). Thereafter, the exposed portion is subjected to a development process, a cleaning process, and a post baking process (see (d)).

The passivation layer 12 is formed by performing an etching process using an etching solution on the passivation layer 12 that is exposed after the predetermined portion 14 of the photoresist 13 is removed through the above-described process. A local opening 15 is formed in the portion corresponding to the middle void pattern (see (e)).

Thereafter, the remaining photoresist 12 is removed through a strip process to complete formation of the void pattern in the passivation layer 11 (see (f)).

Photomask or photoresist is used as a consumable during the above-described process, and the maintenance cost is high, and wastewater is generated by using chemicals such as etching solution, which causes environmental pollution and wastewater treatment problems. In addition, the photoresist applied on the passivation layer may contaminate the undesired portions, and as the above-described process requires many processes, the manufacturing time is long and the manufacturing cost is high.

Therefore, the above-described problem can be solved by forming a pore pattern on the back passivation layer of the solar cell using the laser etching apparatus according to the embodiment of the present invention.

FIG. 5 is a flowchart illustrating a method of forming a pore pattern in a rear passivation layer of a solar cell according to a laser etching technique using a laser etching apparatus according to an embodiment of the present invention.

Referring to FIG. 5A, a passivation layer 11 made of a dielectric material is formed on the back surface of the silicon substrate 10 of the solar cell.

Referring to FIG. 5B, a portion of the passivation layer 11 is removed by irradiating a laser beam to a position where a void pattern is to be formed using a laser etching apparatus. Here, the void pattern may be formed in the passivation layer 11 by adjusting the laser beam to have processing conditions according to the characteristics of the silicon substrate 10.

The characteristics of the silicon substrate 10 affecting the laser processing conditions may be the back surface structure of the silicon substrate.

According to the structure of the back surface of the silicon substrate, a laser beam having suitable conditions may be selected and irradiated to a corresponding position to form a void pattern. The back surface structure may be a saw damage etching (SDE) structure or a textured structure, and accordingly, various laser processing conditions such as laser beam wavelength, laser power, pulse width, and repetition rate may be set. Can be.

As shown in FIG. 4, in the case of forming a void pattern by using a photolithography technique or by screen printing, the surface needs to be flat to obtain a predetermined precision or resolution with respect to the void pattern.

6 is a cross-sectional view of a solar cell having both the front and rear surfaces flat, and FIG. 7 is a cross-sectional view of the solar cell having both the front and rear texture surfaces.

The solar cell shown in FIG. 6 has a surface structure in which both front and rear surfaces have been removed from cutting damage. In this case, the surface reflectivity of light incident through the front surface is about 30% or less, which causes a lot of light loss.

Accordingly, in the case of the current solar cell, a surface structure having a concave-convex structure composed of pyramids is implemented through a texturing process to increase the light trapping effect on the front surface as shown in FIG. 7. In this case, a textured pyramid structure is formed not only on the front side but also on the back side of the silicon substrate. In this textured surface structure, the surface reflectivity is reduced to about 10% or less and the optical absorption path is long (see FIG. 6A), thereby increasing the efficiency of the solar cell.

However, in order to form a void pattern on the rear surface by using photo etching technology or screen printing, it was necessary to make the rear surface flat. To this end, a process of forming a mask on the rear surface and a process of removing the mask had to be added.

On the other hand, by using the laser etching apparatus according to the embodiment of the present invention, it is possible to form a void pattern directly on the textured surface without making the back surface flat. Since the rear surface has a textured surface structure, an additional process of making the rear surface flat through a separate process is unnecessary, thereby simplifying the process. In addition, since the back surface has a textured surface structure, the amount of light that is reflected or scattered through the back reflection layer into the silicon substrate may be increased, thereby increasing the efficiency of the solar cell.

Laser processing conditions may be set differently depending on whether the back surface of the solar cell is a structure that is removed from cutting damage or a textured structure. In addition, at the rear surface having a textured structure, laser processing conditions may be set in more detail according to the size of the pyramid, the shape of the pyramid, and the like.

Thereafter, the back electrode is formed, and the metal constituting the electrode is diffused into the silicon substrate 10 of the solar cell through a firing process, thereby manufacturing a highly efficient and thinned solar cell.

8 is a block diagram of a laser etching apparatus according to an embodiment of the present invention, FIG. 9 is an embodiment of the scan unit, and FIG. 10 is another embodiment of the scan unit.

Referring to FIG. 8, the laser etching apparatus 100 includes a laser oscillator 110, a beam expanding unit 120, a beam forming unit 130, a scanning unit 140, a projection unit 150, and a stage unit 160. It may include.

The laser oscillator 110 includes a laser medium, a pumping unit, a switching unit, and the like to output a laser beam having a predetermined pulse width. The laser beam oscillated by the laser oscillator 110 may be a continuous wave mode or a pulse wave mode.

The wavelength of the laser beam oscillated by the laser oscillator 110 according to the present embodiment may be 126 nm to 2940 nm, has a processing power of 0.3 watts to 10 watts, and has a pulse width of 100 fs to 100 ns at 20 kHz. , Repetition rate may be 100khz to 300khz.

For example, laser processing conditions are shown in Table 1 below. Here, the pulse width and the like unit is ^{ns (nanosecond, 10 -9 s)} , ps (picosecond, 10 -12 s), fs (femtosecond, 10 -15 s).

However, the numerical values relating to the laser wavelength, the processing power, the pulse width, and the repetition rate shown in Table 1 do not mean numerical values in a strict sense, but also mean numerical values in the meanings commonly used by those skilled in the art for laser processing. to be.

Here, as the wavelength of the laser beam is shorter, fine and precise processing is possible in forming the pore pattern of the solar cell, and thus the processing performance is improved, and the longer the wavelength of the laser beam, the lower the price of the system is.

In using the laser beam, laser processing conditions such as wavelength, processing power, pulse width, repetition rate, etc. of the laser beam may be changed according to the back surface structure of the solar cell substrate to be processed.

The beam expanding unit 120 enlarges the size of the laser beam so that a more precise laser beam spot can be formed in the beam forming unit 130 at the rear end.

The beam forming unit 130 processes the size and / or shape of the laser beam spot in accordance with the size and shape of the void pattern to be processed for the laser beam enlarged by the beam expanding unit 120. The energy distribution can be converted to a flat top format to ensure even energy transfer over the processing area.

In this embodiment, each pore may have various shapes such as a circle, an ellipse, and a polygon, and the beam forming unit 130 may change the size and shape of the laser beam according to the size and shape of each pore.

The scan unit 140 corresponds to a focus adjusting unit, and finely horizontally moves the focus of the laser beam on the rear passivation layer of the solar cell.

Referring to FIG. 9, a scan unit 140 according to an embodiment is shown.

The scan unit 140 includes a central portion 210, a rotating member 220, which is a rod-shaped structure having one end fixedly connected to the central portion 210, and a head portion 230 fixedly connected to the other end of the rotating member 220. It is a structure that includes, the first mirror 212 is provided in the central portion 210, the second mirror 232 is provided in the head 230. The laser beam transmitted from the front end component is reflected at the first mirror 212 and reflected back at the second mirror 232 along a path parallel to the rotating member 220 to focus the focusing element 240 (eg, And a solar cell substrate 200 mounted on the stage unit 160 by a projection unit or the like.

Here, the rotating member 220 is rotated in the clockwise or counterclockwise direction along the arrow around the central portion 210, the head portion 230 of the circumference having a radius corresponding to the length of the rotating member 220 The laser beam may be irradiated at some position in the path. The laser beam may be irradiated as shown in FIG. 11 by repeating the rotation of the head unit 230 while moving the stage unit 160 in a direction perpendicular to the path of the head unit 230.

Referring to FIG. 10, a scan unit 140 according to another embodiment is shown.

The scan unit 140 may be provided with two galvano mirrors 250 and 260 facing each other. The first galvano mirror 250 receives and reflects the laser beam and rotates about the first axis according to the driving of the motor 252. The second galvano mirror 252 receives and reflects a laser beam reflected from the first galvano mirror while rotating about a second axis different from the first axis according to the driving of the motor 262. Therefore, the laser beam is a desired point on the stage unit 160 by adjusting the angle between the first axis and the second axis, the degree of rotation of the first galvano mirror 250, and the degree of rotation of the second galvano mirror 260. It is possible to be investigated. In this embodiment, each axis of the two galvano mirrors is moved by the scan unit 140 and the respective galvano mirrors are rotated by the scan unit 140 according to the positions of the pores to be formed in the rear passivation layer of the solar cell according to a predetermined pattern.

That is, the laser beam is positioned at a position to form a void in the entire solar cell substrate without moving the stage unit 160 using two galvano mirrors or moving the solar cell substrate mounted on the stage unit 160. It is possible to investigate the area scan is possible, there is an advantage that has a high degree of freedom in the pore forming position.

In another embodiment, the scan unit 140 may be configured by a combination of a galvano mirror and a polygon mirror. In the above-described embodiment, one of the two galvano mirrors may be replaced with a polygon mirror.

Here, the laser beam is irradiated to the desired point on the stage unit 160 by adjusting one or more of the angle formed between the rotation axis of the galvano mirror and the rotation axis of the polygon mirror, the degree of rotation of the galvano mirror, and the degree of rotation of the polygon mirror. It is possible. In the present embodiment, the scanning unit 140 moves the respective rotation axes of the galvano mirror and the polygon mirror and rotates the galvano mirror and the polygon mirror in accordance with the positions of the pores to be formed in the rear passivation layer of the solar cell according to a predetermined pattern. Let's do it.

The combination of the galvano mirror and the polygon mirror is also possible to irradiate the laser beam to the position to form the voids on the entire solar cell substrate to scan the area, there is an advantage that has a high degree of freedom in the pore formation position.

In another embodiment, the scan unit 140 includes one of a galvano mirror and a polygon mirror to perform one-way scan. In this case, the stage 160 moves in a direction different from the scanning direction of the galvano mirror or the polygon mirror (for example, in a vertical direction) to irradiate a laser beam to a position where a void is to be formed in the entire solar cell substrate. Can be.

After positioning the laser beam to be irradiated to a specific position by the scanning unit 140, the projection unit 150 focuses the laser beam finely adjusted to irradiate a predetermined position of the rear passivation layer of the solar cell. The projection unit 150 may be configured of an fexeta lens, a telecentric lens, or the like. The fexeta lens or the telecentric lens may allow the laser beam to be irradiated substantially vertically at a predetermined position. The projection 150 must be focused so that the laser beam can be accurately irradiated to a predetermined position of the rear passivation layer where the target void pattern is to be formed. Here, the projection unit 150 may be composed of a single lens, a lens group of a combination of several convex and concave lenses may be composed of, or may be composed of a combination of one or more lenses and other optical systems. .

The etching is performed at the portion irradiated with the laser, so that the distance between the projection unit 150 and the stage unit 160 may be adjusted so that a focal point may be formed on the rear passivation layer. In addition, when the depth to be etched is deeper than the focal depth of the laser, it is necessary to operate to adjust the position of the lens by the etched depth as the etching proceeds.

The stage 160 is mounted with a solar cell substrate having a back passivation layer to be etched by the laser etching apparatus 100 according to the present embodiment. The stage 160 moves two-dimensionally on a plane along the X-axis or Y-axis, or moves up and down along the Z-axis to the solar cell substrate on which the focus of the laser beam passing through the projection 150 is placed on the stage 160. You can make it fit.

In the present embodiment, the laser oscillator 110, the beam expanding unit 120, the beam forming unit 130, the scanning unit 140, and the projection unit 150 are optically connected. Optical phenomena include various phenomena such as reflection, diffraction, and refraction of light. Here, 'optically connected' means that light emitted from one component is received by the other component by various optical phenomena. it means. Each component may be directly optically connected or may be optically connected by an optical system including a mirror, a lens, or the like that transmits or reflects a laser beam.

11 is a flowchart illustrating a method of forming voids in the manufacture of a solar cell using a laser etching apparatus according to an embodiment of the present invention.

The silicon substrate on which the back passivation layer is formed is mounted on the stage unit 160 (step S300). Since the silicon substrate is preferably mounted so that the laser beam can be irradiated to the rear surface of the silicon substrate, the back surface of the silicon substrate may be inverted and mounted on the upper surface of the stage unit 160.

A silicon substrate serving as the base of the solar cell is prepared (step S302), and a passivation layer is formed on the rear surface of the silicon substrate (step S304). In this process, a general texturing process, a diffusion process, an anti-reflection film manufacturing process, and the like may be further included in manufacturing a solar cell.

The substrate characteristics of the silicon substrate of the solar cell to be processed are determined using a laser etching apparatus (step S310). The substrate characteristic to be determined is the back surface structure of the silicon substrate to which the laser beam is to be irradiated.

In this way, the substrate characteristics are analyzed to set the laser processing conditions or to adjust the laser processing conditions which are already set when forming the void pattern in a subsequent process.

In the step S312 of analyzing the back surface structure, the wavelength, the processing power, the pulse width, the repetition rate, and the like of the laser beam are determined according to whether the back surface of the silicon substrate of the solar cell is a cut damaged or textured structure. Optimized laser processing conditions can be set.

According to another embodiment, the substrate characteristics of the solar cell may be determined or analyzed before step S300 in which the solar cell is provided to the stage unit 160 of the laser etching apparatus.

The silicon substrate of the solar cell mounted on the stage unit 160 is irradiated with a laser beam to form a void pattern (step S320).

The laser beam is oscillated (step S322), the substrate characteristics are determined in advance, and the laser beam is adjusted according to the set laser processing conditions (step S324). The laser beam is focused and irradiated to a position to be removed in the rear passivation layer by scanning in accordance with a predetermined gap pattern (step S326) (step S328). In the above process, the scan may be performed by the scan unit 140 including the galvano mirror, and the condensing and irradiation of the laser beam may be performed by the projection unit 150.

By repeating steps S326 to S328, a desired pore pattern is formed on the entire silicon substrate of the solar cell mounted on the stage unit 160.

After one or more pores are formed and the pore pattern is completed for the entire silicon substrate of the solar cell, a subsequent process for manufacturing the solar cell is performed (step S330).

In general, a metal electrode for collecting the photogenerated charge is formed on the front and rear of the solar cell (step S332). By twisting a very thin line like a net, the mesh is made into a structure that allows particles to fall out, and by screening with a screen having a certain pattern by blocking the part of the mesh with an emulsion (emulsion coating) where the particles do not want to fall out. Formation of the metal electrode is possible. The paste drawn on the screen mask in which the opening is formed may be rubbed with a squeeze to form a metal pattern on the surface of the substrate.

The metal paste used to form the electrode of the solar cell may be silver (Ag) as a metal for front contact, aluminum (Al) as a metal for forming a rear electric field, AgAl with 3% aluminum as a bus bar metal for rear soldering, and the like. .

Then, the metal electrode is dried and heat treatment is performed through a sintering process (step S334) to make the chemical contact with silicon while reducing the specific resistance of the metal itself, thereby completing the formation of the metal electrode.

In the present invention, a highly efficient thinned solar cell has been described assuming a solar cell having a rear point contact structure, but in addition, the rear point contact heterojunction structure, a simple back electrode structure (simplified back-point) Solar cells such as contact) can be formed using the above-described laser processing apparatus.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be understood that the invention may be varied and varied without departing from the scope of the invention.

1 is a cross-sectional view of a solar cell with a thick silicon substrate.

2 is a cross-sectional view of a solar cell having a thin silicon substrate.

3 is a cross-sectional view of a solar cell having a back point contact structure.

Figure 4 is a flow chart of a method for forming a pore pattern on the back passivation layer of the solar cell according to the conventional photolithography technique.

FIG. 5 is a flowchart illustrating a method of forming a void pattern in a rear passivation layer of a solar cell according to a laser etching technique using a laser etching apparatus according to an embodiment of the present invention. FIG.

6 is a cross-sectional view of the solar cell is flat both front and back.

7 is a cross-sectional view of a solar cell having a structure in which both the front and back surfaces are textured.

8 is a block diagram of a laser etching apparatus according to an embodiment of the present invention.

9 is a diagram illustrating an embodiment of a scan unit;

10 is a view showing another embodiment of a scanning unit.

11 is a flow chart of a method for forming voids in manufacturing a solar cell using a laser etching apparatus according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

1, 3, 10: silicon substrate 2: back electrode

4: point contact electrode 5, 11: passivation layer

15: void 100: laser etching device

110: laser oscillation unit 120: beam expanding unit

130: beam forming unit 140: scanning unit

150: projection unit 160: stage unit

Claims (8)

In the laser etching apparatus for forming a void in the back passivation layer during solar cell manufacturing, A stage unit for mounting the silicon substrate of the solar cell on which the rear passivation layer is formed; A laser oscillator for oscillating a laser beam adjusted according to the back surface structure of the silicon substrate; A beam forming unit for modifying the size and shape of the spot of the laser beam according to the size and shape of the cavity; A scanning unit scanning the laser beam to irradiate a position of the void according to a void pattern in which at least one void is arranged; And a projection unit for condensing and irradiating the laser beam scanned by the scan unit. The method of claim 1, The back surface structure is a laser etching apparatus, characterized in that the saw damage etching (SDE) structure. The method of claim 1, And the back surface structure is a textured structure. The method of claim 3, And the laser oscillator oscillates the laser beam finely adjusted according to one or more of the size and shape of the pyramid formed on the back surface of the silicon substrate. In the solar cell manufacturing method of forming a void using a laser etching device, (a) preparing a silicon substrate having a passivation layer formed on a rear surface thereof; (b) analyzing passivation layer information for the passivation layer; (c) adjusting laser processing conditions of the laser etching apparatus according to the analyzed passivation layer information; (d) forming a pore pattern in the passivation layer using the laser etching device. The method of claim 5, The back surface structure is a solar cell void forming method, characterized in that the saw damage etching (SDE) structure. The method of claim 5, And the back surface structure is a textured structure. The method of claim 7, wherein The step (c) is a method for forming voids in the solar cell, characterized in that to fine-tune the laser processing conditions in accordance with one or more of the size and shape of the pyramid formed on the back surface of the silicon substrate.

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