KR101032601B1 - Method for treating the surface of silicone sollar cell using high frequency pluse - Google Patents

Abstract

PURPOSE: A silicon solar battery cell using a high frequency pulse and method for processing the surface of a cell are provided to form a porous surface on the silicon solar battery cell, thereby increasing the non reflection rate of a poly-crystal silicon solar battery cell. CONSTITUTION: A silicon solar battery cell is etched by a potassium hydroxide 10% solution. The silicon solar battery cell is activated in a mixed solution in which a hydrofluoric acid 5% solution or a nitric acid 15% solution are mixed. A porous surface is formed on the silicon solar battery cell by a high frequency electrolytic process. The high frequency electrolytic process uses high frequency pulse power of 10,000~50,000Hz. The silicon solar battery cell is dried in a hot wind drying room.

Description

Method for treating the surface of silicone sollar cell using high frequency pluse}

The present invention is a surface treatment method of a silicon solar cell, and more particularly, by forming a nano-sized porous surface on the surface through electrochemical electrolytic treatment of the silicon surface to increase the specific reflectivity of the polycrystalline silicon solar cell, the solar cell The purpose is to increase the dust collection efficiency of the cell.

A solar cell is a device that converts light energy into electrical energy. The solar cell has a structure different from that of chemical cells, and can be called a physical cell.

A solar cell generates electricity using two types of semiconductors, a P-type semiconductor and an N-type semiconductor.

The principle of the solar cell is that when light shines on the solar cell, electrons and holes are generated inside, and the generated charges move to the P and N poles, which causes a potential difference (photovoltaic power) between the P and N poles. At this time, if a load is connected to the solar cell, a current flows.

This is called a photoelectric effect.

Solar jersey modules draw power by connecting multiple solar cells in series or in parallel in large systems.

1 is a schematic diagram of a cell, module, and array of a solar cell.

The cell is the smallest unit that generates electricity, the module is the smallest unit that draws electricity and is half the size of the front door.

An array is a series of panels fitted in series or in parallel. A subarray is a unit that organizes several modules for ease of maintenance.

Symbol (a) denotes a cell, symbol (b) denotes a module, and symbol (c) denotes an array.

In order to effectively utilize solar cells, it is essential to manufacture solar cells with high conversion efficiency while lowering production costs.

Surface treatment method for increasing the conversion efficiency of the existing polycrystalline silicon battery cell is vacuum deposition method to form a TiO ₂ anti-reflection film to form a specific reflectivity to reduce the specific reflectivity or surface by using chemical etching (HF, KOH) Surface treatment is mainly used to increase the antireflection efficiency by forming the roughness of.

However, in the case of the vapor deposition method, the production cost is high and the problem of mass production is accompanied, so that the productivity and economical efficiency are lowered, and in the case of the chemical treatment method, the effect of increasing the non-reflective efficiency is not limited.

Although studies have been made to form porous silicon surfaces in polycrystalline solar cells using some anodization, problems have arisen due to differences in the uniformity of the surface and the degree of refinement thereof.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and by increasing the specific reflectivity of a polycrystalline silicon solar cell by forming a nano-sized porous surface on the surface through electrochemical electrolytic treatment, the dust collection efficiency of the solar cell is increased. will be.

As a means for solving the problem of the present invention, the silicon solar cell is subjected to a process of one step etching process, two step activation process, three step high frequency electrolytic treatment process and four step drying process, wherein the high frequency electrolytic treatment process is 10,000 to 50,000 Hz. of the high frequency pulse by using the power and an insoluble anode plate the surface of a silicon cell as a (+) pole (-) current in an electrolyte composed mainly of sodium fluoride and hydrofluoric acid, ammonium sulphate and the pole density of 1~3A / dm ² The electrolytic treatment is carried out at a current density to form a porous surface having a size of 300 to 600 nm.

In the high efficiency surface treatment method of silicon solar cell using high frequency pulse according to the present invention, polycrystalline silicon solar cell is formed by forming nano-sized porous surface through electrochemical electrolytic treatment on silicon surface as compared to conventional vacuum deposition and chemical treatment methods. By increasing the specific reflectivity of the cell can increase the dust collection efficiency of the solar cell.

1 is a schematic diagram of a cell, module, array of a solar cell.
2 is a process chart showing a surface treatment process of a silicon solar cell using a high frequency pulse.
3 is a device schematic diagram of a high frequency electrolytic treatment process of the present invention.
Figure 4 is a surface comparison photo of a silicon solar cell using a high frequency pulse according to the current density difference.
5 is a schematic diagram of a pulse power supply.

Hereinafter, the surface treatment process of the silicon solar cell using the high frequency pulse of the present invention with reference to the accompanying drawings in detail as follows.

2 is a process chart showing a surface treatment process of a silicon solar cell using high frequency pulses.

First, in a one step process, the solution is etched in a 10% solution of potassium hydroxide (KOH) to remove acid that is corroded to the surface of the silicon battery cell.

In a two-step activation process, the silicon battery cell is immersed in a hydrofluoric acid (HF) or nitric acid (HNO _{3 )} solution.

The activation process is a process performed to remove impurities present on the surface of a silicon wafer cell and to form a uniform porous film by forming only pure silicon on the surface. Those skilled in the art are not described in detail in the present invention because they are processes that can be performed within general conditions and ranges.

The porous surface of 300-600nm size is formed through the three-step high frequency electrolytic treatment process, and the process is completed by the four-step drying process.

Drying conditions in the drying step are performed in a hot air drying furnace at 80 to 100 ° C.

Between each process, water washing is constituted to remove impurities or to remove the solution of the entire process.

Detailed description of the high frequency electrolytic treatment will be described later.

3 is a device schematic diagram of a high frequency electrolytic treatment process of the present invention.

As shown in FIG. 3, the silicon battery cell is immersed in the electrolytic cell 1 containing the electrolyte, and the insoluble negative electrode plate 4 is connected to the negative electrode of the pulse power supply 7.

The insoluble negative electrode plate 4 is alternatively used among platinum (Pt) or titanium (Ti).

In addition, the electrolytic cell 1 is provided with a circulation pump 5 for circulation of the electrolyte solution 2.

The electrolyte solution 2 uses 10 to 12 wt% sodium fluoride, 25 to 30 wt% hydrofluoric acid, and 3 to 5 wt% ammonium sulfate, and optionally adds about 0.01 wt% of anionic surfactant.

The rest is ion exchanged water.

The silicon solar cell 3 is connected to the (+) electrode with an electric wire or a busbar. The temperature of the electrolyte solution 2 is 20 to 25 ° C., the current density is 1 to 3 A / dm ² , and the applied frequency is 10,000 to 50,000. It is a high frequency of Hz.

Although the applied voltage can adopt either a DC voltage and an AC voltage, it is preferable to use an AC power supply in consideration of the following process for the antimicrobial film of this invention.

Since the device schematic diagram shown in FIG. 3 is the same as the schematic diagram of the anodic oxidation process, the temperature control device 6 is provided for maintaining the temperature because the temperature maintenance of the electrolyte solution rising during the oxidation reaction is very important like the anodization process.

In addition, in order to promote smooth agitation and surface oxidation of the electrolyte solution 2, the electrolyte solution is stirred using a circulation pump 5 as an air stirring device.

Symbol In denotes an electrolyte inlet and Out denotes an electrolyte outlet.

<Examples>

A P-type polycrystalline silicon wafer (3.3 cm x 3.3 cm) of 1 to 10 占 Ωcm was immersed in a 10% solution of potassium hydroxide as a sample and etched. A 5% solution of hydrofluoric acid (HF) and 15% mixed solution of nitric acid (HNO ₃ ) Activated for 3 minutes and pretreated.

Electrolytic treatment conditions were porous electrolytic treatment in the composition and conditions shown in Table 1.

The result of the reflectance of the surface-treated surface is shown.

division
Electrolytic Treatment Condition Electrolyte composition
Type of power
Temperature
(℃)
Pulse period
(ms)
Duty cycle
(%)
reflectivity
(600nm) Sodium fluoride (wt%) Foshan
(wt%) Ammonium sulfate
(wt%) Example 1 10 25 0 pulse 50 0.5 50 15 Example 1 10 25 235 pulse 50 0.5 60 12 Example 1 10 25 5 pulse 50 0.5 70 12 Example 1 12 25 3 pulse 50 0.5 80 10 Example 1 12 30 3 pulse 50 1.0 50 10 Example 1 12 30 3 pulse 50 1.0 60 10 Comparative Example 1 0 25 0 DC - - - 25 Comparative Example 2 5 30 0 DC - - - 20

As described above, Comparative Examples 1 to 2 under the same conditions as in Examples 1 to 10 were conducted.

4 is a surface comparison photograph of a silicon solar cell using a high frequency pulse according to the difference in current density.

4, ① current density 1A / dm ² , ② current density 1.5A / dm ² , ③ current density 2A / dm ² , and ④ current density 3A / dm ² .

Current density of 1 to 3 A / dm ² It can be seen that when the surface treatment is good.

In the case of DC power supply, ion polarization phenomenon is generated by oxygen generated on the silicon surface during electrolytic treatment, so that uniform surface treatment is impossible.

A typical AC power source is a sine wave (sign) wave, and in Korea, 60 GHz is the frequency of an AC power source.

5 is a schematic diagram of a pulse power supply.

Duty cycle (%) = t _on / (t _on + t _off ) × 100

t _on : time when current is applied

t _off : Time when no current is applied

As shown in FIG. 5, the pulse power source is a square wave, not a sine wave, and thus, the voltage current is turned to the opposite polarity to give the time to turn off the power for a predetermined time, thereby reducing the ion polarization phenomenon of the plating solution (antibacterial metal electrodeposition). It is an excellent power source that serves to uniformly fill the film in narrow holes such as a pore layer.

In addition, in the case of the pulse power supply, unlike the AC power supply, the antimicrobial metal is uniformly electrodeposited according to the duty cycle as shown in FIG. 5, and in the case of the pulse period (ms), the frequency represents 1 / pulse period As a result, the frequency of the high frequency is very short and the effect is large.

Therefore, the duty cycle and period in the pulse power source is not a selectable value but the most important factor for uniformly filling the film pore layer of the silicon solar cell.

1. Electrolyzer 2. Electrolyte
3. Silicon Solar Cell 4. Negative Plate
5. Circulation pump device 6. Temperature controller
8. Pulse Power Supply

Claims (3)

In the surface treatment method of a silicon solar cell,
Etching the first step silicon solar cell in a 10% solution of potassium hydroxide (KOH);
Activating a silicon solar cell subjected to a two-step etching process in a 5% solution of hydrofluoric acid (HF) or a 15% mixed solution of nitric acid (HNO ₃₎ ;
A high frequency electrolytic treatment process for forming a porous surface having a size of 300 to 600 nm in a silicon solar cell subjected to a three-step activation process;
A drying step of drying the silicon solar cell subjected to the four-step high frequency electrolytic treatment in a hot air drying chamber at 80 to 100 ° C .;
Consisting of
In the high frequency electrolytic treatment process, the surface of the silicon solar cell 3 is made of (+) and the insoluble anode plate 4 is made of (-). High frequency pulses characterized by electrolytic treatment at 20-25 ° C. with an electric current density of 1 to ³ A / dm ² in an electrolyte solution 2 consisting of sodium, 25 to 30 wt% hydrofluoric acid and 3 to 5 wt% ammonium sulfate. Surface treatment method of the silicon solar cell using.
delete The method of claim 2,
The insoluble negative electrode plate (4) is a surface treatment method of a silicon solar cell using high frequency pulses, characterized in that can be used alternatively of platinum (Pt) or titanium (Ti).

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