KR20150045806A - Cell and manufacturing method for the solar cell - Google Patents

Abstract

Disclosed are a solar cell capable of forming a solar cell absorption layer with high efficiency and low costs by a wet method; and a manufacturing method thereof. The cell includes a silicon substrate and a nanowire structure which is formed on the substrate by electrochemically etching a nano metal catalyst formed by an electroless plating method using silver nitrate (AgNO3) solution by using hydrogen peroxide (H2O2) solution. The nanowire structure is formed by an electrochemical etching process by using the H2O2 solution of 0.25M concentration.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a battery,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell or a secondary battery, and more particularly, to a method for manufacturing a silicon solar cell which is economical and highly efficient by forming a silicon nanowire structure, and a battery manufactured by the method.

The structure of a silicon solar cell is composed of an antireflection film (AR coating) for allowing solar light to be absorbed into the silicon substrate and an antireflection film (AR coating) inside the solar cell , And a P-layer). In a silicon solar cell, a p-type junction is formed by forming an n-type semiconductor by diffusing a Group 5 element on its surface based on p-type silicon. When the solar light is absorbed on the substrate where the pn junction is formed, an electronholepair (EHP) is formed and freely moves. When the electron enters the electric field generated by the pn junction, the hole (+) is p- the electrons move to the n-type and a potential is generated, and the generated electron mobility causes a current to flow to the external conductor through the electrodes at both ends.

The output of the solar cell is composed of the product of the short-circuit current J _SC (the output current when V = 0 on the current-voltage curve) and the open-circuit voltage V _OC (the output voltage when I = 0 on the current-voltage curve). The conversion efficiency of converting all the light from the sun into electricity is to increase the short-circuit current or open-circuit voltage, or to close the fill factor (FF) to 1, which indicates the approximation of the output voltage curve to a square (J _SC × V _OC ) do.

J _{SC increases} mainly as the reflectance for light irradiated to the solar cell decreases, and V _OC increases as the degree of recombination of carriers (electrons and holes) decreases. FF is close to 1 when the resistance in n-type and p-type semiconductors or between these and the electrode is small. From this, it can be seen that J _SC , V _OC and FF, which determine the efficiency of the solar cell, are controlled by different factors.

As a method of improving the efficiency of the solar cell, a method of suppressing the reflectance of the sunlight has been devised, and a dry concave convex texture is mainly formed by the vapor phase method to reduce the reflectance to about 10-20%. However, Is being studied.

Conventionally, there is a method of forming an antireflection film on a surface of a solar cell or forming a nanostructure on the surface of a solar cell by improving the photovoltaic efficiency characteristic by maximizing reduction of the solar light reflectance for increasing the efficiency of the solar cell. As a method for forming the antireflection film, silicon nitride (SINx) may be deposited on the light receiving portion of a solar cell by a chemical vapor deposition (CVD) method, and a silicon nitride To form an antireflection film. The wet etching method is mainly studied for the low production cost of the solar cell among the dry etching method and the wet etching method.

As a method of forming the nanostructure, there is a Vapor-Liquid-Solid (VLS) method, which is mainly manufactured by growing nanowires, and a method of forming a nanostructure by a wet-dry etching process using a porous mask .

When nanowires are fabricated by the conventional VLS method, the array of nanowires becomes irregular. Even when the optimized solar cell passivation (doping and TCO process) is applied, An etching method has been proposed as a method for arraying nanowires with limitations. In addition, the method of forming a nanostructure using a porous mask is advantageous in that it can form a uniform arrangement and a vertical nanostructure, but is limited because it is difficult to form a polycrystalline silicon thin film on a low-cost substrate such as a glass substrate.

As described above, it has been confirmed that the antireflection layer of the silicon absorbing layer manufactured by the conventional method is a relatively expensive production technique, which is suitable for small-scale production and has a limit to the lowering of the reflectance directly affecting the solar light efficiency.

According to embodiments of the present invention, a method for manufacturing a low-cost high efficiency solar cell or an absorbing layer of a secondary battery through a wet process, and a battery manufactured thereby are provided.

The battery according to the embodiments of the present invention includes a silicon substrate and a nano metal catalyst formed by electroless plating using a silver nitrate solution on the substrate, the nanowire structure formed by electrochemical etching using a hydrogen peroxide solution , And the nanowire structure is formed by electrochemically etching using a hydrogen peroxide solution with a concentration of 0.25M.

According to one aspect, the metal catalyst layer may be formed by reacting with a silver nitrate solution at a concentration of 10 mM for 60 seconds. The metal catalyst layer may be subjected to an electroless plating process at a temperature of 20 to 30 캜.

According to one aspect, the nanowire structure is formed using an etching solution formed by mixing hydrofluoric acid and hydrogen peroxide, the hydrofluoric acid has a concentration of 4.8M, and the hydrogen peroxide has a concentration of 0.25M. Here, the nanowire structure may be subjected to an electrochemical etching process at a temperature of 25 ° C.

According to another aspect of the present invention, there is provided a method of manufacturing a battery, including: providing a substrate; forming a metal catalyst layer on the substrate using an electroless plating solution mixed with a silver nitrate solution and a fluoric acid; And forming a nanowire structure by electrochemically etching the catalyst layer with an etching solution mixed with hydrogen peroxide solution and hydrofluoric acid.

According to one aspect, the step of providing the substrate includes a first cleaning step of cleaning the substrate with a mixed solution of ammonia, hydrogen peroxide and water in a volume ratio of 30: 30: 150 by volume at 80 DEG C for 10 minutes, A second cleaning step of cleaning the substrate with a mixture of hydrofluoric acid and water at a volume ratio of 4: 200 at room temperature for 30 seconds, and cleaning the substrate with pure water (DI), and a second cleaning step of cleaning the substrate with hydrochloric acid, hydrogen peroxide, A tertiary cleaning step of washing the solution with a mixed solution of water and water at a volume ratio of 30: 30: 150 at 85 DEG C for 10 minutes, washing with pure water (DI), and drying with nitrogen can be performed.

According to one aspect of the present invention, the forming of the metal catalyst layer may be performed by using a mixed solution of 4.8 M of hydrofluoric acid and 10 mM of silver nitrate at a temperature of 20 to 30 ° C for 30 to 60 seconds.

According to one aspect, the step of forming the nanowire structure is performed at 25 ° C using an etching solution comprising hydrogen fluoride mixed with 4.8 M of hydrofluoric acid and any one of concentrations of 0.5M, 0.25M, and 0.125M . Here, in the step of forming the nanowire structure, the hydrogen peroxide may have a concentration of 0.25M.

As described above, according to the embodiments of the present invention, in the absorption layer for determining the efficiency of the solar cell or the secondary battery cell, the absorption layer having the anti-reflection function is devised, By forming the nanowire structure, it is possible to manufacture a solar cell with higher efficiency than the planar silicon solar cell by increasing the absorption rate of light and increasing the current value of the solar cell and controlling the area of the pn junction according to the density of the wire.

In addition, since the silicon nanowire structure uses an electroless method and an electrochemical metal catalytic etching method, it can be mass-produced at low cost and reproducibly manufactured when a solar cell substrate is manufactured.

FIGS. 1A and 1B are diagrams for explaining the formation of a nano-metal catalyst according to the temperature of a silver nitrate solution in a solar cell manufacturing method according to an embodiment of the present invention. FIG. 1A is at 20 ° C., The results are shown in Fig.
FIG. 2 is a SEM photograph showing a nanowire structure fabricated according to an etching reaction time of a hydrogen peroxide solution in an embodiment of the present invention. FIG.
FIGS. 3A to 3C are graphs of reflectance according to reaction time according to the concentration of hydrogen peroxide solution in a solar cell manufacturing method according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments will be described in detail with reference to the accompanying drawings, but the present invention is not limited to or limited by the embodiments. In describing the embodiments, a detailed description of well-known functions or constructions may be omitted so as to clarify the gist of the present invention.

Hereinafter, a battery and a manufacturing method thereof according to an embodiment of the present invention will be described in detail with reference to FIGS. 1A to 3C.

The battery according to this embodiment may be, for example, a solar cell. According to these embodiments, a battery having a nanowire structure maximizing efficiency can be manufactured by forming an absorption layer having an antireflection function without forming a separate antireflection film on the substrate.

Therefore, in the fabrication of nanowires, embodiments of the present invention include a method of controlling the formation of silver (Ag) nanoparticles on a single crystal p-type silicon substrate by an electroless plating method and a method of etching a substrate using an electrochemical metal catalytic etching The nanowire structure can be manufactured economically and reproducibly.

Silicon nanowire manufacturing process The reaction principle is to immerse a silicon wafer in a silver nitrate solution (AgNO ₃ ) to form nano-silver (Ag) particles on the surface of a silicon substrate by electroless plating, : A hole due to a reduction reaction of a hydrogen peroxide (H ₂ O ₂ ) solution as an etching solution is formed on the surface of the silicon substrate through the metal catalyst, and the generated hole is diffused into the silicon substrate through the metal catalyst, And the silicon substrate is dissolved by hydrofluoric acid (HF) at the interface of the silicon / metal catalyst.

Such a structure increases the path of light incident to the interior of the conventional planar solar cell by forming a nanostructure in a portion absorbing light in the solar cell. As a result, the current value is increased due to the quantum effect such as photon confinement, which ultimately contributes to the high efficiency of the solar cell, and the high cost antireflection (AR) coating used in conventional solar cells This allows a high solar absorption by a very high light trapping effect to be unnecessarily high. In addition, the area where the pn junction is formed in the solar cell can be maximized to several orders of magnitude depending on the density of the wire.

Example 1

The present invention relates to a method of manufacturing a nanowire by forming a silver nanoparticle on a substrate by using an electroless plating method using a single crystal p-type silicon substrate and controlling a substrate etching using an electrochemical metal catalytic etching method, A structure is prepared. In the nanowire manufacturing process, a silicon substrate is cleaned, a metal catalyst is plated on a cleaned substrate by an electroless plating method, an electrochemical etching (etching) is performed on the metal catalyst, and an inorganic metal removal process is performed .

Here, the single crystal p-type silicon substrate is prepared by the following three-step cleaning process. First, in the first stage cleaning, cleaning for removing organic substances from the silicon substrate is required. In the first cleaning, a solution in which ammonia, hydrogen peroxide, and water are appropriately mixed at a volume ratio of 30: 30: 150 is prepared and washed at 80 ° C for 10 minutes. At this time, for efficient cleaning, a mixed solution of ammonia and water is first prepared, and the solution is heated to 80 DEG C, and hydrogen peroxide is titrated to prepare a cleaning solution. Then, the silicon substrate is cleaned for 10 minutes with the solution prepared at such a constant composition and temperature. Next, a mixed solution prepared by mixing hydrofluoric acid and water at a volume ratio of 4: 200 was prepared for efficient removal of the native oxide layer on the silicon substrate subjected to the first cleaning, and the silicon substrate was washed at room temperature for 30 seconds After that, it is washed again with DI to complete the secondary washing. In order to remove metallic inorganic substances on the silicon substrate, a third cleaning is performed. In the third cleaning, a solution prepared by mixing hydrochloric acid, hydrogen peroxide and water at a volume ratio of 30: 30: 150 is prepared and washed at 85 ° C for 10 minutes After washing with DI, dry with nitrogen gun. Here, for efficient cleaning, a mixed solution of hydrochloric acid and water is also prepared at the time of the third rinsing, and the solution is heated at a temperature of 85 ° C, and hydrogen peroxide is titrated thereto to prepare a cleaning solution.

The electroless plating process for the production of metal catalyst of silver nanoparticles is carried out at a temperature of 20 to 30 캜 by mixing 4.8 M of hydrofluoric acid and 10 mM of silver nitrate solution. Specifically, the cleaned silicon substrate is immersed in a reaction vessel containing the electroless plating solution prepared as described above, held for 30 to 60 seconds, and then immersed in DI solution and washed, a silver nano-metal catalyst .

After the nano metal catalyst particles are produced, an electrochemical etching (etching) process is performed to form a nanowire structure. Here, the etching process is performed by etching (etching) at 25 DEG C for 2 minutes, 4 minutes, 6 minutes, and 8 minutes using an etching solution prepared by mixing hydrofluoric acid of 4.8M and hydrogen peroxide of 0.5M, 0.25M, and 0.125M And rinsed with DI solution. To control the reaction time accurately in the electroless and etching process, a tool was prepared so that the silicon substrate could be immersed in the solution and taken out and washed. Although the nanowire structure is formed on the silicon substrate by the electrochemical etching process, cleaning treatment with a nitric acid solution having a constant composition is performed to finally complete the manufacture of the silicon nanowire structure in order to remove the metal catalyst and the foreign substance remaining in the reaction.

According to the embodiment of the present invention, the formation of the nano-metal catalyst and the control of the generation density are possible by controlling the concentration, the temperature and the reaction time of the electroless plating solution. FIGS. 1A and 1B are views for explaining the formation of a nano-metal catalyst according to the temperature of a silver nitrate solution in a solar cell manufacturing method according to an embodiment of the present invention. FIG. 1A shows nanometer metal catalyst particles formed as a single layer on a silicon substrate, in the case of a silver nitrate solution with a temperature of 20 DEG C and a concentration of 10 mM, performed for a reaction time of 40 to 60 seconds. 1B shows the case where the silver nano catalyst particles are formed in a multi-layered structure on the silicon substrate at the same concentration and reaction time of the same solution as in FIG. . In the present invention, particle size and structure of the metal catalyst can be controlled according to the temperature, composition (concentration) and reaction time of the electroless solution. In the above reaction, the silver coated silver particles applied with 10 mM silver nitrate solution are prepared by increasing the solution temperature of the reactor to 20 to 25 ° C. in the range of 25 to 30 ° C. At that time, the reaction of the nanoparticle catalyst particles is very sensitive to the temperature of the solution The reaction is known.

2 is SEM photographs showing the structure of nanowires on silicon electrochemically etched according to one embodiment of the present invention. Referring to FIG. 2, there is shown a nanowire structure on a silicon substrate electrochemically etched by a solution of hydrogen peroxide 0.25M (4 minutes, 6 minutes, 8 minutes) during electrochemical etching. According to FIG. 2, the width and length of the prepared nanowires are increased in proportion to the reaction time, and the nanowires are uniformly dense with a relatively slight aggregation at the top. Although not shown in FIG. 2, it was confirmed that a very uniform nanowire structure was formed even when the reaction time was as short as about 2 minutes. When the concentration of hydrogen peroxide solution was 0.5M, the length of the nanowire was very short and the surface of the top surface was very heterogeneous in a short reaction period of 2 to 4 minutes. In addition, when the concentration of the hydrogen peroxide solution is lowered to 0.125M, the shape of the formed nanowire structure is more uniform than that of the solution having a concentration of 0.5M. However, even if the reaction time is increased, . Therefore, it was confirmed that the most optimal shape of the nanowire structure was formed in the 0.25M concentration solution as described above.

FIGS. 3A to 3C are graphs of reflectance according to reaction time according to the concentration of hydrogen peroxide solution in a solar cell manufacturing method according to an embodiment of the present invention. FIGS. 3A to 3C are graphs showing the results when the nanowire structure was prepared by forming the electroless catalyst metal under the conditions of 10 mM of silver nitrate and 60 seconds, and then performing electrochemical etching with 0.5 M, 0.25 M, and 0.125 M hydrogen peroxide solution, The graphs show the results of measuring the reflectance (absorbance) of the nanowire structure in the solar effective wavelength region according to the time (2 minutes, 4 minutes, 6 minutes, 8 minutes). Referring to the drawings, the reflectance on the average of 3.7 to 8.4% (wavelength range: 300 to 1200 nm) was obtained according to the etching time. In addition, the reflectance was as low as 3.7% in the case of the above-mentioned 0.25M hydrogen peroxide solution and the reaction time of 6 minutes, and also the reflectance was very low in the entire solar wavelength region even under a short reaction time of 2 minutes, It can be seen that the reflectance is improved more than two times as compared with the case where the concentration of the hydrogen peroxide solution is manufactured under the same conditions of 0.5M and 0.125M.

According to the embodiment of the present invention, the silicon nanowire structure can be mass-produced at low cost in manufacturing a solar cell substrate by a wet process. Further, by forming the nanowire, the absorption rate of light is increased, and the area of the pn junction can be controlled according to the increase of the current value of the solar cell and the density of the wire, so that a solar cell with higher efficiency than the conventional planar silicon solar cell can be manufactured have. In particular, by applying the absorbing layer of the nanowire structure to the solar cell, the reflectance of sunlight can be reduced to 5% or less from the conventional 10-20% level, which ultimately contributes to the maximization of the solar light efficiency.

While embodiments of the present invention have been described by way of example with reference to a solar cell, the present invention is not limited thereto, and may be applied to a cathode silicon technology of a secondary battery as well as a solar cell.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. For example, it is to be understood that the techniques described may be performed in a different order than the described methods, and / or that components of the described systems, structures, devices, circuits, Lt; / RTI > or equivalents, even if it is replaced or replaced.

Therefore, other implementations, other embodiments, and equivalents to the claims are also within the scope of the following claims.

Claims (10)

A silicon substrate; And
A nanowire structure formed by electrochemical etching using a hydrogen peroxide solution on a nano-metal catalyst formed by electroless plating using silver nitrate solution on the substrate;
Lt; / RTI >
Wherein the nanowire structure is formed by electrochemically etching using a hydrogen peroxide solution with a concentration of 0.25M.
The method according to claim 1,
Wherein the metal catalyst layer is reacted with a silver nitrate solution at a concentration of 10 mM for 60 seconds.
3. The method of claim 2,
Wherein the metal catalyst layer is subjected to an electroless plating process at a temperature of 20 to 30 캜.
The method according to claim 1,
The nanowire structure is formed using an etching solution formed by mixing hydrofluoric acid and hydrogen peroxide,
The hydrofluoric acid has a concentration of 4.8M, and the hydrogen peroxide has a concentration of 0.25M.
5. The method of claim 4,
Wherein the nanowire structure is subjected to an electrochemical etching process at a temperature of 25 < 0 > C.
Providing a substrate;
Forming a metal catalyst layer on the substrate using an electroless plating solution in which silver nitrate solution and hydrofluoric acid are mixed; And
Electrochemically etching the metal catalyst layer with an etching solution mixed with hydrogen peroxide solution and hydrofluoric acid to form a nanowire structure;
≪ / RTI >
The method according to claim 6,
Wherein providing the substrate comprises:
A first cleaning step of cleaning the substrate with a mixed solution of ammonia, hydrogen peroxide and water in a volume ratio of 30: 30: 150 at 80 DEG C for 10 minutes;
A second cleaning step of cleaning the substrate with the mixed solution of hydrofluoric acid and water at a volume ratio of 4: 200 in the first cleaned state at room temperature for 30 seconds, and cleaning the substrate with pure water (DI); And
A second cleaning step of cleaning the substrate with the second cleaned substrate in a mixed solution of hydrochloric acid, hydrogen peroxide and water at a volume ratio of 30: 30: 150 at 85 ° C for 10 minutes, washing the substrate with pure water (DI)
Is carried out.
The method according to claim 6,
Wherein the forming of the metal catalyst layer comprises:
4. The method for producing a cell according to claim 1, wherein the solution is prepared by mixing a solution of 4.8 M of hydrofluoric acid and 10 mM of silver nitrate in a solution at a temperature of 20 to 30 DEG C for 30 to 60 seconds.
The method according to claim 6,
Wherein forming the nanowire structure comprises:
4. The method for producing a battery according to claim 1, wherein the etching solution is a mixture of hydrofluoric acid of 4.8M and hydrogen peroxide having a concentration of 0.5M, 0.25M or 0.125M at 25 占 폚.
10. The method of claim 9,
Wherein forming the nanowire structure comprises:
Wherein the hydrogen peroxide has a concentration of 0.25M.

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