KR101482745B1 - Method of preparing a solar cell - Google Patents

Abstract

The present invention relates to a method of manufacturing a solar cell. In the method of manufacturing a solar cell according to the present invention, a low contact resistance printing layer and an electrode printing layer are sequentially formed on one surface of a silicon substrate through electrohydrodynamic printing and then simultaneously fired to form a low contact resistance metal layer and an electrode layer , A solar cell can be manufactured with a simpler process, thereby enabling the provision of a solar cell having an improved performance.

Description

METHOD OF PREPARING A SOLAR CELL [0002]

The present invention relates to a method of manufacturing a solar cell, and more particularly, to a method of manufacturing a solar cell using electrohydrodynamic printing and a co-firing process.

Solar cells can be classified into silicon solar cells, thin film solar cells, dye-sensitized solar cells, and organic polymer solar cells depending on the kinds of main constituents. Among them, silicon solar cells have higher photoelectric conversion efficiency than other cells, It is known that production is the highest in the world.

In recent years, techniques for lowering the production cost or increasing the production efficiency, such as using a low-grade raw material for the production of silicon solar cells, have been continuously reported. As part of this, the proportion of the cost of the electrode material consumed in forming the conductive pattern Interest in the cost competitiveness is increasing.

In this connection, a screen printing method and an inkjet printing method using a piezoelectric element have been applied to an electrode forming process of a silicon solar cell. However, in the recent trend in which a silicon substrate having a thin thickness is gradually used, the screen printing method in which a mechanical pressure is applied to a silicon substrate has a problem that the breakage rate of the silicon substrate increases. The ink-jet printing method using the piezoelectric element is a digital printing technique, and consumable parts such as screen plates are not required, and the consumed amount of the electrode material can be minimized, so that productivity higher than that of the screen printing method can be secured . However, since the inkjet printing method has a limitation on the size of droplets that can be formed, efficiency in forming the electrode pattern is somewhat lowered, and there is a restriction on the viscosity of the electrode material that can be jetted, .

On the other hand, a metal paste including a glass frit is used for electrode formation of a silicon solar cell. However, since the electrode material including glass frit exhibits a low electrical conductivity after the heat treatment process for forming the electrode, a low contact resistance metal layer between the silicon substrate and the electrode Is applied. The metal layer having a low contact resistance may be formed by forming a metal layer (for example, a nickel layer or the like) by a method such as electroless plating and then performing a heat treatment (annealing) Is converted into nickel silicide or the like).

In order to prevent the metal layer formed by plating or the like from being oxidized before annealing, the formation of the metal layer having low contact resistance requires expensive equipment because it is performed under a vacuum or an inert gas atmosphere, and a continuous annealing process There is a problem that it is difficult to carry out. Further, since the metal layer formed by the above-described plating or the like is different in composition to be formed according to the temperature condition of the annealing process by Ni ₂ Si, NiSi, NiSi ₂ or the like, the temperature condition of the annealing process is restricted Follow.

Particularly, in the conventional general manufacturing method, since the process of printing and heat-treating the electrode material (metal paste including glass frit, etc.) after the formation of the metal layer with low contact resistance (plating and annealing) And productivity is deteriorated.

 High-resolution electrohydrodynamic jet printing, JANG-UNG PARK et al. Nature Materials, 2007.

Accordingly, the present invention overcomes the limitations of the screen printing method, the ink jet printing method using a piezoelectric element, and the like, which are applied to the electrode forming process, and also a method of manufacturing a solar cell through a more simplified and efficient process without expensive equipment .

According to the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming on a surface of a silicon substrate a low contact resistance printed layer containing nickel by electrohydrodynamic printing;

Forming an electrode print layer on the low-contact-resistance printed layer by electrohydrodynamic printing; And

Forming a low contact-resistance metal layer including nickel silicide and an electrode layer by firing a silicon substrate having the low-contact-resistance printed layer and the electrode printed layer formed thereon;

A method for manufacturing a solar cell is provided.

Here, the low contact-resistance printing layer may be formed according to a process of printing and drying the nickel-containing ink on the silicon substrate through electrohydrodynamic printing.

In addition, the electrode print layer may contain an ink containing at least one metal selected from the group consisting of silver (Ag), gold (Au), copper (Cu), aluminum (Al), tin (Sn) Printed on the low contact resistance printing layer through electrohydrodynamic printing and dried.

The ink used for forming the low-contact-resistance printed layer or the electrode printed layer may each have a viscosity of 10 to 50,000 cP.

The firing can be performed at a temperature of 550 to 1000 캜 for 5 to 30 minutes; The firing can be performed in an oxygen atmosphere.

The silicon substrate may further include an anti-reflection layer. In this case, the manufacturing method of the solar cell according to the present invention may further include forming an electrode-shaped opening by etching the antireflection layer of the silicon substrate, wherein the low contact resistance printing layer is formed on the opening .

The method of manufacturing a solar cell according to the present invention can minimize the risk of breakage of a silicon substrate and consumption of an electrode material by applying electrohydrodynamic printing when printing an electrode pattern, Can be continuously printed. Furthermore, the method of manufacturing a solar cell according to the present invention can simultaneously perform a heat treatment (sintering) process necessary for forming a low contact-resistance metal layer and an electrode layer under high temperature and oxygen atmosphere, A solar cell can be manufactured through a simpler continuous process.

FIG. 1 and FIG. 2 are process flowcharts schematically showing a manufacturing method of a solar cell according to an embodiment of the present invention.
3 is a TEM-EDS analysis result of a cross section of a solar cell according to an embodiment of the present invention.
FIGS. 4A and 4B show results of comparative observation of electrode shapes of a solar cell according to an embodiment of the present invention.
5 illustrates an electro-luminescence image of a solar cell according to an embodiment of the present invention.

Hereinafter, a method of manufacturing a solar cell according to embodiments of the present invention will be described.

Prior to that, unless explicitly stated throughout the present specification, the terminology is for reference only, and is not intended to limit the invention.

And, the singular forms used herein include plural forms unless the phrases expressly have the opposite meaning.

Also, as used herein, the term " comprises " embodies specific features, regions, integers, steps, operations, elements or components, and does not exclude the presence of other specified features, regions, integers, steps, operations, elements, It does not.

The term "a low contact resistance metal layer" as used throughout the present specification refers to a layer formed between a substrate and a substrate of a solar cell. By reducing the contact resistance between the electrode and the substrate, Means a layer that can be improved. For example, a low contact resistance metal layer generally applied to a silicon solar cell may include nickel silicide (NiSi) or the like, and such a low contact resistance metal layer may include a layer containing nickel (hereinafter referred to as a " nickel layer & Followed by heat treatment (annealing). Here, as a method of forming the nickel layer, electroless plating or the like is known, and the nickel layer changes as Ni ₂ Si, NiSi, NiSi ₂ or the like depending on the heat treatment temperature. At this time, the coating layer formed by printing an ink containing nickel in a predetermined electrode pattern is referred to as a " low contact resistance printing layer ", which is converted into a low contact resistance metal layer by heat treatment (firing).

The term 'electrode print layer' as used throughout this specification refers to a coating layer formed by printing an electrode material, that is, an ink containing metal for electrodes, in a predetermined electrode pattern, which is converted to an 'electrode layer' by heat treatment .

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art to which the present invention pertains. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.

The present inventors have found that when electrohydrodynamics printing is applied to a process of forming an electrode pattern during repeated research on a solar cell, it is possible to overcome the limitations of the conventional screen printing method and inkjet printing method Respectively. In particular, when electrohydrodynamic printing is applied to the method of manufacturing a solar cell according to the present invention, the heat treatment (baking) process required for forming the low-contact-resistance metal layer and the electrode layer can be performed simultaneously at high temperature and oxygen atmosphere, It is confirmed that the solar cell can be manufactured through the simplification of the continuous process using the existing heat treatment equipment without the expensive equipment.

According to this embodiment of the present invention,

Forming a low contact resistance printed layer comprising nickel on one side of a silicon substrate by electrohydrodynamic printing;

Forming an electrode print layer on the low-contact-resistance printed layer by electrohydrodynamic printing; And

Forming a low contact-resistance metal layer including nickel silicide and an electrode layer by firing a silicon substrate having the low-contact-resistance printed layer and the electrode printed layer formed thereon;

A method for manufacturing a solar cell is provided.

That is, as shown in FIG. 1, a method for manufacturing a solar cell according to the present invention comprises sequentially forming a low contact-resistance resistive print layer and an electrode print layer on one surface of a silicon substrate through electrohydrodynamic printing, .

In this regard, a screen printing method or an inkjet printing method using a piezoelectric element has been applied to a process of forming an electrode pattern on a silicon substrate. However, in the recent trend of using a thin silicon substrate for manufacturing a solar cell, the screen printing method in which a mechanical pressure is applied to a silicon substrate has a problem that the breakage rate of the silicon substrate increases. On the other hand, the ink-jet printing method using the piezoelectric element is a digital printing technique, and consumable parts of the electrode material can be minimized while consumable parts such as screen plates are not required, and productivity can be secured as compared with the screen printing method . However, since the inkjet printing method has a limitation on the size of droplets that can be formed, efficiency in forming the electrode pattern is somewhat lowered, and there is a restriction on the viscosity of the electrode material that can be jetted. As a result, .

Meanwhile, in the method of manufacturing a solar cell according to the present invention, electrohydrodynamic printing is applied to a process of forming an electrode pattern. The electrohydrodynamic printing is a non-contact printing method in which ink is pulled out by using a potential difference between a nozzle and a substrate, so that the risk of damage to the silicon substrate can be minimized. Furthermore, since the electrohydrodynamic printing is performed in a digital manner, the amount of electrode material used can be optimized, thereby reducing waste of raw materials. Since the electrohydrodynamic printing is less affected by the ink type and viscosity characteristics than the general inkjet printing method, the viscosity range of the applicable electrode material is wide and continuous printing is possible by using various materials.

In particular, the method of manufacturing a solar cell according to the present invention is characterized in that a low contact-resistance resistive print layer and an electrode print layer are sequentially formed on one surface of a silicon substrate through electrohydrodynamic printing and then heat-treated (sintered) do.

That is, in order to form a low contact-resistance metal layer, a method of forming a metal layer such as a nickel layer by a method such as electroless plating and then converting the metal layer to nickel silicide or the like by heat treatment (annealing) has been used. However, in order to prevent the metal layer formed by electroless plating or the like from being oxidized prior to the heat treatment process, heat treatment is performed in a vacuum or an inert gas atmosphere, so that expensive equipment is required.

Also, the composition of the nickel layer varies depending on the temperature conditions of the heat treatment process, such as Ni ₂ Si, NiSi, and NiSi ₂ . The heat treatment conditions for forming the nickel silicide (NiSi) having the lowest specific resistance (for example, about 300 to 700 ° C, a vacuum or an inert gas atmosphere) , Which is also possible in an oxygen atmosphere). Therefore, the heat treatment step has to be carried out separately, thereby complicating the entire process and lowering the production efficiency.

On the other hand, in the method of manufacturing a solar cell according to the present invention, a low contact-resistance printed layer including nickel is formed on one surface of a silicon substrate through the electrohydrodynamic printing, and an electrode print layer is formed thereon. Accordingly, the low-contact-resistance printed layer can be protected by the electrode print layer, and even if the heat treatment is performed in an oxygen atmosphere, the possibility of oxidation is low. Therefore, the conventional solar cell manufacturing method according to the present invention can use existing heat treatment equipment such as a continuous belt firing furnace without using expensive equipment for forming a vacuum or an inert gas atmosphere. Further, since the low-contact-resistance printed layer can be protected by the electrode print layer, nickel suicide can be stably formed even at a firing temperature (for example, about 550 ° C or higher) for the electrode print layer, (Heat treatment) process can be collectively performed.

According to the present invention, there is provided a method of manufacturing a semiconductor device, comprising: forming a low contact-resistance printed layer including nickel on one surface of a silicon substrate by electrohydrodynamic printing; A step of forming an electrode print layer by electrohydrodynamic printing on the low contact-resistance printed layer may be performed.

Herein, the silicon substrate can be applied without any particular limitation, as is common in the technical field to which the present invention belongs. In addition, the silicon substrate may have a textured surface, and preferably an anti-reflection layer such as silicon nitride may be further formed.

2, in the manufacturing method according to the present invention, the step of forming the electrode-shaped opening by etching the antireflection layer of the silicon substrate is performed first, It is preferable to form a low contact-resistance printed layer containing nickel to be described later on the opening. In this way, the low-contact-resistance printed layer is formed on the opening (preferably in the concave space formed by the formation of the opening), and the electrode printed layer is formed thereon, It may be beneficial to sufficient protection of the layer.

In the present invention, the low contact-resistance printed layer containing nickel may be formed by printing and drying the nickel-containing ink on the silicon substrate (or the opening) through electrohydrodynamic printing. The electrode print layer may be formed according to a process of printing and drying the ink including the electrode metal on the low contact resistance printing layer through electrohydrodynamic printing. The electrode metal may be at least one metal selected from the group consisting of silver (Ag), gold (Au), copper (Cu), aluminum (Al), tin (Sn), and alloys thereof.

The low contact resistance printing layer and the electrode printing layer are each formed through electrohydrodynamic printing. In the printing process, the voltage applied to the electrophotographic printing apparatus, the distance between the silicon substrate and the nozzle, the jetting speed, etc. are controlled , It is possible to realize a precise line width which is smaller than the nozzle size but is required.

In addition, since the electrophoretic printing process is less affected by the kind and viscosity characteristics of ink than a general inkjet printing process, there is an advantage that a low viscosity ink and a high viscosity ink can be continuously printed using one apparatus . Accordingly, in the present invention, inks having a viscosity of 10 to 50,000 cP can be used for forming the low-contact-resistance printed layer and the electrode printed layer containing nickel, respectively. Here, the viscosity of the ink can be adjusted in an appropriate range according to the characteristics of each layer to be formed. For example, a low-viscosity ink may be used because the low-contact-resistance printed layer containing nickel is preferably formed to be relatively thin. Further, since the electrode print layer is preferably formed to have a relatively high aspect ratio, a high viscosity ink can be used.

Meanwhile, the nickel-containing ink for forming the low-contact-resistance printed layer may include nickel, a binder resin, an organic solvent, and the like. The binder resin and the organic solvent may be conventional ones, Do not. However, besides the nickel, metals capable of forming a metal layer having a low contact resistance may be applied.

The ink for forming the electrode print layer may be a metal suitable for an electrode for a silicon solar cell such as silver (Ag), gold (Au), copper (Cu), aluminum (Al), tin An alloy of one or more metals selected from the group consisting of alloys of the metals; In addition, conventional glass frit, binder resin, organic solvent, and the like can be further included. The glass frit may be included in the ink to penetrate the antireflection layer formed on the silicon substrate. However, the larger the content of the glass frit is, the lower the electrical conductivity is, so that the content thereof is advantageously small. In the case of using a silicon substrate having an antireflection layer formed thereon, the manufacturing method of the present invention is characterized in that after the opening is formed by etching the antireflection layer, a low contact resistance printing layer is formed on the opening, Since the resistance can be minimized, the content of the glass frit can be reduced, and thus a solar cell having excellent cell characteristics can be obtained.

According to the present invention, a step of simultaneously forming a low contact-resistance metal layer including nickel silicide and an electrode layer by heat-treating (firing) the silicon substrate on which the low-contact-resistance printed layer and the electrode printed layer are formed .

As described above, in the manufacturing method according to the present invention, the low contact resistance printed layer including nickel formed on one surface of the silicon substrate can be protected from oxygen and high temperature environment by the electrode print layer. Accordingly, unlike the previous fabrication methods, the fabrication method according to the present invention can be performed without using expensive equipment for forming a vacuum or an inert gas atmosphere, by using an existing heat treatment apparatus such as a continuous belt firing furnace in an oxygen atmosphere, A firing process can be performed. Also, nickel silicide can be stably formed even at a firing temperature (for example, about 550 DEG C or higher) for the electrode print layer, so that the firing process can be performed collectively (i.e., simultaneously).

The firing may be performed at a temperature of 550 to 1000 ° C for 5 to 30 minutes, preferably at a temperature of 750 to 1000 ° C for 10 to 30 minutes, more preferably 750 to 950 ° C ≪ / RTI > for 10 to 20 minutes. That is, when the temperature is too high or the time is too long in the firing process, nickel is oxidized or nickel silicide having a high resistivity is formed, so that the contact resistance can be increased. Conversely, if the temperature is too low or too short, the nickel silicide may not sufficiently be formed, the contact resistance may increase, and the fill factor may be lowered. Therefore, in consideration of the efficiency of the simultaneous firing in the present invention and the performance of the finally obtained cell, it is advantageous that the firing process is performed under the above-mentioned temperature and time conditions.

Through such a baking process, the low contact-resistance resistive print layer containing nickel can be converted to a low contact resistive metal layer including nickel silicide, and at the same time, the electrode print layer can be converted to an electrode layer.

The front electrode may be formed through each of the above steps. In addition, conventional steps for manufacturing the solar cell may be performed before or after each step. For example, after the baking step, the back electrode paste is printed on the other surface of the silicon substrate, and then the baking process is performed to obtain the substrate having the front electrode and the rear electrode formed thereon.

Hereinafter, preferred embodiments of the present invention will be described in order to facilitate understanding of the present invention. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

Example  One

A 156 mm polycrystalline silicon wafer was placed in a tube furnace and phosphorus (P) was doped into the silicon wafer through a diffusion process using POCl ₃ at about 880 ° C to form an emitter layer having a sheet resistance of about 80 Ω / . Then, a silicon nitride film was deposited on the emitter layer by a PECVD method to form an antireflection layer having a thickness of about 80 nm.

Then, an opening having a depth of about 80 nm was formed by printing an electrode pattern having a width of about 60 탆 on the antireflection layer by a screen printing method using an etching paste and etching.

On the other hand, a nickel ink for electrohydrodynamic printing (about 40% by weight of nickel; About 1% by weight of a binder resin (alkylphenol-formaldehyde copolymer); About 50% by weight of an organic solvent (ethyl cellosolve); About 9% by weight of additives such as co-solvents, dispersants and the like; An ink viscosity of about 200 cP) was prepared. Then, the nickel ink was printed on the opening by electrohydrodynamic printing to form a low contact resistance printing layer (thickness of about 80 nm, width of about 60 탆), which was dried at about 60 캜 for 10 minutes.

In addition, the ink for electrophysiological printing (about 80% by weight; About 5% by weight of a binder resin (ethylcellulose); About 10% by weight of an organic solvent (butyl carbitol acetate); About 0.5% by weight glass frit; About 4.5 wt% of additives such as co-solvents; Ink viscosity of about 20,000 cP]. Then, the silver ink was printed on the low-contact-resistance printed layer by electrohydrodynamic printing to form an electrode print layer (thickness of about 25 mu m, width of about 80 mu m), which was dried at about 270 DEG C for 10 minutes .

Aluminum paste (manufacturer: Toyo, product name: ALSOLAR) was screen-printed on the opposite side of the silicon substrate on which the low-contact-resistance printed layer and the electrode printed layer were formed with a rear electrode pattern and dried at about 200 ° C for 10 minutes.

Then, the roughened silicon substrate was baked in a belt baking furnace at about 900 캜 for about 10 minutes to obtain a solar cell having a front electrode having a thickness of about 23 탆 and a width of about 80 탆.

Comparative Example  One

A solar cell was prepared in the same manner as in Example 1, except that the step of forming the low contact-resistance printed layer using the nickel ink was not performed.

Comparative Example  2

A solar cell was manufactured in the same manner as in Example 1, except that the firing in the belt firing furnace was performed at about 400 캜 for 10 minutes.

Comparative Example  3

And the electrode print layer was formed on the low contact-resistance metal layer formed by the heat treatment at a temperature of about 400 캜 in a vacuum atmosphere immediately after formation of the low contact-resistance resistive printing layer, A battery was prepared.

Comparative Example  4

And the electrode print layer was formed on the low contact-resistance metal layer formed by the heat treatment immediately after formation of the low contact-resistance resistive print layer at a temperature of about 900 캜 under a vacuum atmosphere. In this way, A battery was prepared.

Comparative Example  5

A solar cell was manufactured in the same manner as in Example 1, except that screen printing was applied instead of electrohydrodynamic printing for forming the low-contact-resistance printed layer and the electrode printed layer, respectively.

Test Example  One

(Confirmation of formation of nickel silicide)

The cross-sectional components of the solar cell according to Example 1 were analyzed through TEM-EDX analysis, and the results are shown in FIG. As shown in FIG. 3, it was confirmed that nickel silicide was formed between the silicon substrate of the solar cell according to Example 1 and the electrode layer.

Test Example  2

(Confirmation of shape of electrode according to printing process)

For the solar cell according to Example 1 and Comparative Example 5, the shape of the front electrode was confirmed using an optical microscope (manufacturer: Olympus), and the results are shown in FIGS. 4A and 4B.

As a result, as shown in FIG. 4A, the front electrode of the solar cell according to Example 1 was formed through electrohydrodynamic printing, and it was confirmed that the spreading was small and the linear shape was well formed. On the other hand, as shown in FIG. 4B, it was confirmed that the front electrode of the solar cell according to Comparative Example 5 was formed through screen printing and spread, and the height of sentence due to the screen mesh mark was not constant. When the electrode is formed in a spread form as in Comparative Example 5, it may have a bad influence on the cell characteristics due to light blocking and electrode bending.

Test Example  3

(Electro Luminance Image)

Electro Luminance Image was photographed for the solar cell according to Example 1 and Comparative Example 4, and the result is shown in FIG. It can be confirmed that the electro-luminescence image exhibits better electrical resistance characteristics of the solar cell as the light is brighter.

As can be seen from FIG. 5, it was found that Example 1 (FIG. 5A) was brighter than Comparative Example 4 (FIG. 5B). That is, it can be confirmed that the solar cell of Example 1 has excellent electrical characteristics such as a contact resistance portion and a series resistance portion, and it can be predicted that the solar cell can exhibit improved efficiency.

Test Example  4

(Cell performance measurement)

Example 1 and Comparative Examples 1 to about 5 solar cells according to, lamp source is using a solar simulator's ABET a _{150W Xenon arc J sc (mA /} ㎠), V oc (V), FF (%) , And E _ta (%) were measured. The results are shown in Table 1 below.

J _sc (mA / cm 2) V _oc (V) FF (%) E _ta (%) Example 1 34.71 0.618 77.4 16.6 Comparative Example 1 25.61 0.592 28.6 4.3 Comparative Example 2 28.55 0.590 27.3 4.6 Comparative Example 3 34.15 0.603 56.5 11.6 Comparative Example 4 34.87 0.600 45.8 9.6 Comparative Example 5 34.29 0.608 77.0 16.1

As can be seen from Table 1, the solar cells (Comparative Example 1 and Comparative Example 2) in which the low contact resistance metal layer is not introduced or the low contact resistance printing layer is fired at a low temperature (Comparative Example 1 and Comparative Example 2) And the efficiency was low. In addition, when the low-contact-resistance printed layer was exposed to a high temperature without protection of the electrode print layer (Comparative Example 3 and Comparative Example 4), the nickel silicide or the oxidized nickel layer with high resistivity was formed. In addition, as shown in Electro Luminance Image, it was confirmed that the efficiency was lower than that of Example 1 due to an increase in electrical resistance in the case of screen printing (Comparative Example 5).

Claims (8)

Forming a low contact resistance printed layer comprising nickel on one side of a silicon substrate by electrohydrodynamic printing;
Forming an electrode print layer on the low-contact-resistance printed layer by electrohydrodynamic printing; And
Forming a low contact-resistance metal layer including nickel silicide and an electrode layer by firing a silicon substrate having the low-contact-resistance printed layer and the electrode printed layer formed thereon;
Wherein the method comprises the steps of:
The method according to claim 1,
Wherein the low contact resistance printing layer is formed according to a process of printing and drying the nickel-containing ink on the silicon substrate through electrohydrodynamic printing.
The method according to claim 1,
Wherein the electrode print layer comprises an ink containing at least one metal selected from the group consisting of silver (Ag), gold (Au), copper (Cu), aluminum (Al), tin (Sn) Wherein the low-contact-resistance printing layer is formed by dynamically printing and printing on the low-contact-resistance printing layer.
The method according to claim 2 or 3,
Wherein the ink has a viscosity of 10 to 50,000 cP.
The method according to claim 1,
Wherein the firing is performed at a temperature of 550 to 1000 DEG C for 5 to 30 minutes.
The method according to claim 1,
Wherein the firing is performed in an oxygen atmosphere.
The method according to claim 1,
Wherein the silicon substrate further comprises an antireflection layer.
8. The method of claim 7,
Further comprising the step of forming an electrode-shaped opening by etching the antireflection layer of the silicon substrate,
And the low contact-resistance printed layer is formed on the opening.

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