KR101151413B1 - Solar cell having multimple anti-reflection film and manufacturing method thereof - Google Patents

Abstract

A solar cell comprising a double antireflection film and a method of manufacturing the same are provided. In the solar cell forming method comprising a double anti-reflection film, forming an emitter layer on a silicon substrate, comprising nickel (Ni) / copper (Cu) / silver (Ag) on the formed emitter layer Forming a front electrode comprising: depositing an antireflection film having a zinc sulfide (ZnS) layer and a magnesium fluoride (MgF ₂ ) layer on a portion where the front electrode is not formed on the emitter layer; and And heat treating the double anti-reflection film together.

Description

SOLAR CELL HAVING MULTIMPLE ANTI-REFLECTION FILM AND MANUFACTURING METHOD THEREOF

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a solar cell having a double antireflection film and a method of manufacturing the same, and more particularly, a double antireflection film which simplifies the manufacturing process and has good battery characteristics by simultaneously heat treating a plurality of films including the double antireflection film. It relates to a solar cell having a and a method of manufacturing the same.

Recently, as the prediction of depletion of existing energy sources such as oil and coal is increasing, interest in alternative energy to replace them is increasing. Among them, solar cells are particularly attracting attention because they are rich in energy resources and have no problems with environmental pollution. Solar cells include solar cells that use steam to generate steam for spinning turbines, and solar cells that convert the photons into electrical energy using the properties of semiconductors. Refers to photovoltaic cells (hereinafter referred to as solar cells).

Referring to FIG. 1, which shows a basic structure of a solar cell, the solar cell has a junction structure of a p-type semiconductor 101 and an n-type semiconductor 102 like a diode, and when light is incident on the solar cell, Interaction with the materials that make up the semiconductor causes electrons with negative charge and electrons to escape, creating holes with positive charge, and as they move, current flows. This is called a photovoltaic effect. Among the p-type 101 and n-type semiconductors 102 constituting the solar cell, electrons are attracted toward the n-type semiconductor 102 and holes are pulled toward the p-type semiconductor 101. The electrodes 103 and 104 are bonded to the n-type semiconductor 101 and the p-type semiconductor 102, respectively, and when the electrodes 103 and 104 are connected by wires, electricity flows to obtain power.

The output characteristics of such a solar cell are generally evaluated by measuring an output current voltage curve using a solar simulator, and the maximum output Pm is the point where the product Ip × Vp of the output current Ip and the output voltage Vp becomes the maximum on the curve. The value obtained by dividing Pm by the total light energy incident on the solar cell (S × I: S is the device area and I is the intensity of light irradiated to the solar cell) is defined as the conversion efficiency η. To increase the conversion efficiency η, increase the short-circuit current Isc (output current when V = 0 on the current voltage curve) or open voltage Voc (output voltage when I = 0 on the current voltage curve) or the square of the output current voltage curve. You should increase the fill factor (FF), which is close to. The closer the value of FF to 1, the closer the output current voltage curve is to the ideal square and the higher the conversion efficiency η. Isc mainly affects the absorbance or reflectance of the solar cell with its irradiated light, Voc affects the degree of recombination of carriers (electrons and holes), and FF affects the resistance in or between n- and p-type semiconductors or between electrodes. Receive

In general, in order to reduce the reflectance of light in a solar cell, an antireflection layer is used, or a method of minimizing the area covering sunlight when forming an electrode terminal is used. Among them, various researches on antireflection layers capable of achieving high reflectance have been conducted. Currently, a method of reducing a reflectance by forming a silicon nitride antireflection film on an emitter in front of a solar cell has been developed and widely used. However, there is a problem that it is difficult to improve the efficiency of the solar cell while simplifying the manufacturing process of the solar cell because a plurality of heat treatment processes are required for manufacturing the solar cell including the anti-reflection film.

On the other hand, as a prior art, Korean Laid-Open Patent Publication No. 2003-0079265 discloses the invention of “high efficiency solar cell and its manufacturing method”, and shows a double film structure of single crystal silicon as a passivation layer and silicon nitride as an antireflection film. It relates to a solar cell manufacturing technology to be used. However, even in the case of the prior art, it is required to go through a plurality of heat treatment processes to form a plurality of double film structure, there was a difficult problem to expect improved efficiency.

Therefore, a solar cell manufacturing technology that can form a double anti-reflection film of the solar cell more effectively to simplify the manufacturing process of the solar cell, and further improve the FF value and conversion efficiency while lowering the reflectance to sunlight, have.

Some embodiments of the present invention provide a double anti-reflection film, which can form a double anti-reflection film of the solar cell more effectively, simplify the manufacturing process of the solar cell, and improve the FF value and conversion efficiency while lowering the reflectance to sunlight. It has a solar cell and its manufacturing method.

As a technical means for achieving the above technical problem, the first aspect of the present invention, forming an emitter layer on a silicon substrate, forming a front electrode on the formed emitter layer, Forming a double anti-reflection film on the portion where the front electrode is not formed on the emitter layer, and heat treating the front electrode and the double anti-reflection film together, forming a solar cell comprising a double anti-reflection film It may provide a method.

Further, the second aspect of the present invention provides a silicon substrate, an emitter layer formed on the silicon substrate, a front electrode formed on a portion of the emitter layer, and a portion on which the front electrode on the emitter layer is not formed. It includes a double anti-reflection film, wherein the front electrode and the double anti-reflection film is heat-treated by one process, it can provide a solar cell having a double anti-reflection film.

According to the problem solving means of the present invention described above, in order to form a solar cell having a double anti-reflection film by performing a heat treatment on a plurality of films in one process, the manufacturing process of the solar cell is simplified, and at the same time It is possible to improve the FF value and conversion efficiency while lowering the reflectivity to light.

1 is a view showing the basic structure of a conventional solar cell.
2 is a diagram illustrating an example of a solar cell in which a double anti-reflection film is formed according to an embodiment of the present invention.
3 is a detailed flowchart of a method of manufacturing a solar cell having a double anti-reflection film according to an embodiment of the present invention.
4 is a detailed flowchart of a method of forming a front electrode and a double anti-reflection film according to an embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "electrically connected" with another part in between . In addition, when a part is said to "include" a certain component, which means that it may further include other components, except to exclude other components unless otherwise stated.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a diagram illustrating an example of a solar cell in which a double anti-reflection film is formed according to an embodiment of the present invention.

As shown in FIG. 2, in the solar cell having a double anti-reflection film according to an embodiment of the present invention, an n-type emitter layer 20 may be formed on the entire surface of the p-type silicon substrate 10. In addition, the anti-reflection film 30 may be formed on the n-type emitter layer 20, and the anti-reflection film 40 may be formed on the anti-reflection film 30. Here, the anti-reflection films 30 and 40 have a high refractive index of 2.2 to 2.6 so that the light reflected from the upper layer and the light reflected from the lower layer can effectively cause destructive interference with each other. It is preferably formed using a material having an upper anti-reflection film 40 is formed using a low refractive index material of between 1.3 and 1.6.

The double anti-reflective films 30 and 40 may be formed of, for example, MgF ₂ / ZnS, MgF ₂ / TiO ₂ , SiO ₂ / SiN, MgF ₂ / CeO ₂ , but are not limited thereto.

In addition, a plurality of grooves are formed from the surface of the anti-reflection film 40 until the top surface of the emitter layer 20 is exposed and electrically connected to the n-type emitter layer 20 by filling the grooves with a conductive material. The front electrode 50 may be formed, and the rear electrode 60 may be formed on the rear surface of the p-type silicon substrate 10.

In the solar cell according to an embodiment of the present invention, in manufacturing a solar cell having a double anti-reflection film (30.40) by simultaneously heat-treating a plurality of films, it is possible to simplify the manufacturing process and shorten the manufacturing time of the solar cell, The FF and efficiency characteristics of a solar cell can be improved.

Hereinafter, a method of manufacturing a solar cell having a double anti-reflection film according to an embodiment of the present invention will be described with reference to FIG. 3.

3 is a detailed flowchart of a method of manufacturing a solar cell having a double anti-reflection film according to an embodiment of the present invention.

Step S100 is a step of cleaning the silicon substrate. In operation S100, the silicon substrate may be textured to form a pyramid structure on the surface of the substrate to increase the number of reflections generated by the pyramid structure, thereby increasing the light generated current. In addition, in step S100, for example, the silicon substrate is texturized with a solution of Na ₂ CO ₃ and then immersed in DHF (Diluted HF) solution for several seconds through a cleaning process using the RCA II method. Impurities and native oxides on the surface can be removed.

Step S200 is a step of forming an emitter layer and an oxide film on the cleaned substrate. The emitter layer is a fundamental element of silicon solar cells, and collects electrons and holes to generate dislocations and is an important factor that affects the electrode forming process. In step S200, the cleaned substrate may be formed using an POCl ₃ solution to form an emitter having a sheet resistance of about 50 Ω / □ in a normal diffusion furnace. In addition, after removing the surface PSG (phosphorous silicate glass) using a HF solution it is possible to form an oxide film having a thickness of about 250 kPa in a conventional oxidation furnace (oxidation furnace).

Step S300 is a step of forming a back electrode of the solar cell. In step S300, back aluminum may be formed by screen printing to form a back electrode and a back surface filed (BSF). Screen printing is a method of applying paste due to physical contact of squeeze.

Step S400 is a step of forming a front electrode of the solar cell. In operation S400, a mask pattern using a mask aligner may be formed by photo-lithography to form a pattern on which the front electrode is to be formed. In addition, a front electrode may be formed on the formed mask pattern, and a Ni / Cu / Ag electrode including a nickel (Ni) layer, a copper (Cu) layer, and a silver (Ag) layer may be formed as the front electrode. can do.

Step S500 is a step of forming a double antireflection film. The reflective emissive film uses two or more optical thin film materials having different refractive indices, and preferably forms a structure in which the reflectance is close to zero. In addition, the anti-reflection film material should not react with the surface of the solar cell and it is preferable to use a material that can protect the surface of the solar cell. In step S500, a double antireflection film may be deposited, and the front electrode (Ni / Cu / Ag electrode) including the deposited double antireflection film and nickel (Ni) may be simultaneously heat-treated.

Hereinafter, a method of forming a front electrode in step S400 and a method of forming a double anti-reflection film in step S500 will be described with reference to FIG. 4.

4 is a detailed flowchart of a method of forming a front electrode and a double anti-reflection film according to an embodiment of the present invention.

Step S402 is to form a nickel (Ni) plating film. In step S402, a nickel plated film may be formed for use of an electrode in contact with the silicon substrate as a diffusion barrier and an adhesion layer of Cu.

In step S402, a nickel plated film can be formed using an electroless plating method. Specifically, nickel electroless plating is Ni ^{2 +} and H ₂ PO ₂ ^- ions (ion) by using an oxidation / reduction reaction is a metal ion in the plating solution reduced by the oxidation reaction of the reducing agent may be deposited on the blood-coated body.

For nickel plating, it is preferable to use nickel chloride (NiCl ₂ -6H ₂ O) as a main component and sodium hypophosphite (NaH ₂ PO ₂ -H ₂ O) as a reducing agent. In addition, it is possible to maintain a pH of 8.5 ~ 8.7 using an ammonia solution to adjust the pH. During the plating, H ₂ bubbles are formed by the above chemical reaction, but if not removed well, Ni film may be formed on the H ₂ bubbles, so it is preferable to steer at an appropriate rpm. It can also be deposited in an aqueous solution at 85 ° C. for 10 minutes to form a Ni film of about 1-2 μm thick.

Step S404 is a step of forming a copper (Cu) plating film. In step S404, Cu may be deposited as a main electrode of the Ni / Cu / Ag electrode by using electroplating and light-induced plating at the same time. In addition, the main component of the plating solution is preferably made of copper sulfate (Curic sulfate: CuSO ₄ -5H ₂ O) and sulfuric acid (sulfuric acid: H ₂ SO ₄ ). Here, the role of sulfuric acid is to obtain a current density at a low voltage by improving the conductivity of the plating solution.

Step S406 is a step of forming a silver (Ag) plating film. The Ag plated film formed in step S506 may be used for Cu electrode passivation for preventing the oxidation of Cu. In the case of Ag, the atomic mass is 107.87, much higher than Cu (63.55), and used for electrode passivation. In addition, since the formed Cu plating film can collect electrons efficiently, Ag can be plated more efficiently by using light-induced plating. In addition, the main components of the aqueous solution is preferably silver cyanide (silver cyanide), potassium cyanide (potassium cyanide).

In an embodiment of the present invention, the Ni / Cu / Ag electrode is formed by a plating method to increase the purity of the metal and improve the aspect ratio (height / width), thereby increasing the light receiving area capable of absorbing light. The resistance can be reduced. In addition, by using Cu having high electrical conductivity as the main electrode, the efficiency of the solar cell can be improved and the cost of forming the metal electrode can be reduced.

Step S502 is a step of depositing a double anti-reflection film. In step S502, preferably zinc sulfide (ZnS) and magnesium fluoride (MgF ₂ ) may be continuously deposited in a vacuum deposition method to minimize the light reflected on the surface of the solar cell. Zinc sulfide (ZnS) is an anisotropic material exhibiting a refractive index of 2.36 at 600 nm, and magnesium fluoride (MgF ₂ ) has a high transmittance in the long wavelength range from vacuum ultraviolet rays of 120 nm to infrared rays of 9000 nm, and low refractive index material in visible light. As the material is mainly used for anti-reflective coating. In addition, in step S502, the thickness of the zinc sulfide (ZnS) layer may be deposited at 560 kPa, and the thickness of magnesium fluoride (MgF ₂ ) may be deposited at 1060 kPa for the minimum reflectance.

Step S504 is a step of heat-treating each film of the Ni / Cu / Ag electrode and the deposited double antireflection film together. In step S504, the process time can be shortened by simultaneously performing heat treatment of the Ni / Cu / Ag electrode containing nickel (Ni) and the double anti-reflection film to manufacture a solar cell having the double anti-reflection film. In step S510, if the time is too long or the heat treatment temperature is too high in the heat treatment process, Ni diffuses into the Si and shunting path near the PN-junction to lower the open circuit voltage (Voc) of the cell. If the heat treatment time is too short or the heat treatment temperature is too low, the contact resistance may increase, causing a problem that the fill factor (FF) of the battery is lowered. The heat treatment conditions in step S504 can have a significant effect on the solar cell characteristics, in order to form a good solar cell, in one embodiment of the present invention using an annealing furnace (annealing furnace) of 0.8 ~ 1.2 l / min argon It is preferable to perform heat treatment for 25 to 35 minutes at a temperature of 370 to 390 ° C while providing (Ar) gas.

< Experimental Example >

In this experimental example, a boron-doped p-type was used, and a CZ silicon wafer having a crystal orientation of 100, a resistivity of 1 to 5 Ω · cm, a size of 20 × 20 mm ² , and a thickness of 300 μm was used.

First, the silicon substrate is textured with a solution of Na ₂ CO ₃ , followed by a cleaning process using the RCA II method, and then immersed in DHF (Diluted HF) solution for several seconds. native oxide was removed. The cleaned substrate was formed using an POCl ₃ solution to form an emitter layer having a sheet resistance of about 50 Ω / □ in a typical diffusion furnace. In addition, after removing the surface PSG (phosphorous silicate glass) using a HF solution to form an oxide film having a thickness of about 250 kPa in a conventional oxidation furnace (oxidation furnace). In addition, in order to form a back electrode and a back surface filed (BSF), back aluminum was formed by screen printing, and a mask aligner (photo-lithography) was used to form a front pattern. A mask pattern using a mask aligner was formed.

Subsequently, a diffusion barrier and an adhesion layer of Cu were formed using nickel by electroless plating (Nickel plating).

Ni electroless plating is Ni ^{2 +} and H ₂ PO ₂ ^-? Oxidation of the ion is a metal ion in the plating solution reduced by the oxidation reaction of the reducing agent to be used for the reduction reaction to be deposited on the blood-coated body which Ni film was formed on the silicon surface, The process is as follows.

(1) Ni ^{2 +} and H ₂ PO ₂ on a silicon ^{surface-reactant} diffusion of ions, etc.

(2) adsorption of reactants on silicon surface

(3) chemical reaction on the surface

^{_{2H 2 PO 2 - + 2H 2}} O + Ni 2 + → N + H 2 + 4H + + 2HPO 3 2 -

4, the reactants from the surface ^{_{(HPO 3 2 -, H 2}} , H +) desorption

(5) reactants diffuse away from the surface

The experimental example used a nickel _{chloride:: (NaH 2 PO 2 H} 2 O sodium hypophosphite?) (Nickel chloride? NiCl 2 6H 2 O) as a main component and sodium hypophosphite as the reducing agent. In addition, the pH was adjusted to 8.5 to 8.7 using an ammonia solution. In addition, during plating, H ₂ bubbles are formed by the above chemical reaction, and the mixture was stirred at an appropriate rpm to remove them. Further, it was deposited in an aqueous solution at 85 ° C. for 10 minutes to form a Ni film having a thickness of about 1 to 2 μm.

Subsequently, Cu was deposited as a main electrode of the Ni / Cu / Ag electrode by using electro plating and light-induced plating at the same time (Copper elecro & light-induced plating). A plating solution consisting of copper sulfate (CuSO ₄ ? 5H ₂ O) and sulfuric acid (sulfuric acid: H ₂ SO ₄ ) was used as a main component.

Subsequently, Ag was formed using a light-induced plating method for use as a Cu electrode passivation for preventing oxidation of Cu (Silver light-induced plating). At this time, an aqueous solution consisting of silver cyanide and potassium cyanide was used as a main component.

Subsequently, zinc sulfide (ZnS) and magnesium fluoride (MgF ₂ ) were continuously deposited by vacuum deposition in order to reflect the light of the surface to a minimum. In addition, the thicknesses of 560Å and 1060Å were deposited for minimum reflectance.

Subsequently, through the heat treatment process under the conditions shown in Table 1, the heat treatment of the MgF ₂ / ZnS anti-reflection film and the heat treatment of the Ni / Cu / Ag electrode at the same time could be simplified to simplify the manufacturing process, the characteristics shown in Table 2 below The solar cell which could have was manufactured.

Heat Treatment Process Experimental Conditions of Experimental Example equipment Temperature time Gas (Ar: Argon) Annealing furnace 380 ℃ 30min 1 l / min

Characteristics of Solar Cell According to Experimental Example Isc (A) Voc (V) FF (%) Light conversion efficiency (%) 0.15 A 0.6 V 75.84 17.31

< Comparative example >

As a comparative example to the experimental example according to an embodiment of the present invention, Ni electroless plating (electroless plating) and the first heat treatment using a rapid thermal process (RTP) to form a nickel silicide (Ni silicide) Cu / Ag was plated using light-induced electroplating and subjected to a second heat treatment. The MgF ₂ / ZnS double reflecting film was deposited and subjected to a third heat treatment at 400 ° C. for 30 minutes using an annealing furnace.

In the comparative example, a solar cell having the characteristics shown in Table 3 below could be manufactured.

Characteristics of Solar Cell According to Comparative Example Isc (A) Voc (V) FF (%) Light conversion efficiency (%) 0.15 A 0.61 V 75.45 17.36

Therefore, according to the experimental example according to an embodiment of the present invention, not only can the process be more simplified than the comparative example that performs a plurality of heat treatment, but also similar to the comparative example, a solar cell having good cell characteristics It can be seen that it can form.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is shown by the following claims rather than the above description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

10 silicon substrate 20 emitter layer
30: antireflection film 40: antireflection film
50: front electrode 60: rear electrode

Claims (11)

In the solar cell forming method comprising a double anti-reflection film,
Forming an emitter layer on the silicon substrate,
Forming a front electrode on the formed emitter layer,
Depositing a double anti-reflection film on a portion of the emitter layer where the front electrode is not formed, and
Heat treating the front electrode and the double anti-reflection film together;
The front electrode includes a nickel plating film, a copper plating film, and a silver plating film,
The double reflective ring film includes an antireflection film including a magnesium fluoride (MgF ₂ ) layer and a zinc sulfide (ZnS) layer, an antireflection film including a magnesium fluoride (MgF ₂ ) layer and a titanium dioxide (TiO ₂ ) layer, and silicon dioxide ( A method of forming a solar cell, which is one of an antireflection film comprising an SiO ₂ ) layer and a silicon nitride (SiN) layer, a magnesium fluoride (MgF ₂ ) layer, and a cerium oxide (CeO ₂ ) layer.
The method of claim 1,
Forming the front electrode,
Forming a nickel plated film on the emitter layer,
Forming a copper plating film on the formed nickel plating film, and
Forming a silver plating film on the formed copper plating film
Include additional
The heat treatment step, the nickel plated film, the copper plated film, the silver plated film and the double anti-reflection film are heat-treated together, the solar cell forming method.
The method of claim 2,
Forming the nickel plated film, the nickel plated film is formed by using an electroless plating (electroless plating),
The forming of the copper plating film may include forming the copper plating film by using an electroplating method and a light-induced plating (LIP) method.
The forming of the silver plated film may include forming the silver plated film by using a light-induced plating (LIP) method.
The method of claim 2,
Depositing the double anti-reflection film,
A method of forming a solar cell, wherein zinc sulfide (ZnS) and magnesium fluoride (MgF ₂ ) are continuously deposited by a vacuum deposition method.
The method of claim 4, wherein
The heat treatment may be performed by injecting 0.8 to 1.2 l / m of argon (Ar) gas at a temperature of 370 to 390 ° C. for 25 to 35 minutes by using an annealing furnace. The anti-reflection film is heat-treated together, the solar cell forming method.
The method of claim 4, wherein
Forming the emitter layer further comprises forming an oxide layer on the formed emitter layer,
Wherein the oxide film is formed to a thickness of 250 kPa, the zinc sulfide (ZnS) layer is deposited to a thickness of 560 kPa, and the magnesium fluoride (MgF ₂ ) layer is deposited to a thickness of 1060 kPa.
In a solar cell having a double antireflection film,
Silicon substrate,
An emitter layer formed on the silicon substrate,
A front electrode formed on a portion of the emitter layer, and
A double anti-reflection film formed on a portion where the front electrode is not formed on the emitter layer,
The front electrode includes a nickel plating film, a copper plating film, and a silver plating film,
The double anti-reflection film includes an anti-reflection film including a magnesium fluoride (MgF ₂ ) layer and a zinc sulfide (ZnS) layer, an anti-reflection film including a magnesium fluoride (MgF ₂ ) layer and a titanium dioxide (TiO ₂ ) layer, and silicon dioxide ( An antireflection film including an SiO ₂ ) layer and a silicon nitride (SiN) layer, an antireflection film including a magnesium fluoride (MgF ₂ ) layer, and a cerium oxide (CeO ₂ ) layer,
The front electrode and the double anti-reflection film are heat-treated by one process, solar cell having a double anti-reflection film.
The method of claim 7, wherein
The front electrode includes a nickel plating film, a copper plating film, and a silver plating film, wherein the nickel plating film, the copper plating film, the silver plating film, and the double antireflection film are heat treated together. battery.
The method of claim 8,
The double antireflection film is a solar cell having a double antireflection film, wherein zinc sulfide (ZnS) and magnesium fluoride (MgF ₂ ) are continuously deposited by a vacuum deposition method.
The method of claim 9,
The front electrode and the double anti-reflection film were heat-treated together by injecting argon (Ar) gas of 0.8 to 1.2 l / m for 25 to 35 minutes at a temperature of 370 to 390 ° C. using an annealing furnace. A solar cell having a double antireflection film.
The method of claim 9,
An oxide film formed between the emitter layer and the double antireflection film
More,
The oxide film is formed of a thickness of 250 Å, the zinc sulfide (ZnS) layer is formed of a thickness of 560 Å, the magnesium fluoride (MgF ₂ ) layer is formed of a thickness of 1060 Å, solar cell having a double anti-reflection film.

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