KR100677374B1 - Manufacturing method of porous solar cells using thin silicon wafer - Google Patents

Abstract

A porous silicon solar cell formed on a thin plate type silicon substrate and a manufacturing method thereof are provided to obtain aiming thickness and surface reflectivity from the solar cell itself and to improve efficiency of photoelectric energy transformation by forming front and rear porous silicon layers using a wet chemical etching process. A front porous silicon layer(400) is formed on a front surface of a P type silicon substrate by using a first wet chemical etching process. An N type silicon emitter layer(300) is formed on the front porous silicon layer. A rear porous silicon layer(200) is formed on a rear surface of the substrate by using a second wet chemical etching process. An ARC(Anti-Reflective Coating) is formed on the N type silicon emitter layer.

Description

Manufacturing Method of Porous Solar Cells Using Thin Silicon Wafer using Thin Silicon Substrate

1 is a cross-sectional view for explaining a conventional p-n junction separation.

Figure 2 is a process chart for explaining the manufacturing method of the solar cell according to the present invention.

3 is a perspective view for explaining the structural change of the surface according to the porosity change of the porous silicon surface.

4a to 4c are electron micrographs according to the surface porosity of the porous silicon according to the present invention.

5 is a graph showing the reflectance according to the porosity change of the porous silicon surface according to the present invention.

Figure 6 is a graph for explaining the chemical solution composition ratio for forming porous silicon in accordance with the present invention.

Figure 7 is a perspective view for explaining the structure of the solar cell according to the present invention.

8 is a graph showing the electrical characteristics of the solar cell according to the present invention.

Explanation of symbols on the main parts of the drawings

100: front metal electrode 200: antireflection film layer

300: n-type silicon emitter layer 400: front porous silicon layer

500: p-type silicon substrate 600: porous silicon oxide layer

700: rear metal electrode 800: rear field effect layer

The present invention relates to a porous silicon solar cell using a thin silicon substrate and a method of manufacturing the same, and particularly to a porous silicon solar cell using a thin silicon substrate capable of high-efficiency energy conversion by performing a porous treatment using a thin silicon substrate. It is about.

In general, the cost of power generation by a silicon solar cell, which is a device that converts light energy into electric energy, is higher than that of conventional power generation means (eg, hydro, thermal, nuclear, etc.).

As described above, since the cost of generating power by solar cells is high, most of the cost of generating power by solar cells is due to the installation cost of solar cells. The silicon substrate, which is the address material of solar cells, accounts for 60% of the price of solar cells, and the metal electrode It accounts for 20 to 30%, and since the materials are expensive, power generation cost per production power is high.

Therefore, in order to reduce the production cost of the solar cell, it is necessary to increase the energy conversion efficiency while reducing the required thickness of the silicon substrate and the material usage of the electrode metal.

In this regard, in order to reduce the thickness of the substrate in the conventional solar cell manufacturing method, pyramid type surface texture was performed by removing silicon having a thickness of 30 μm or more by etching in a surface texture process.

As described above, the purpose of organizing the surface of the substrate is to increase the light collection effect, to reduce the front reflectance, and to extend the light passing length in the solar cell to increase the utilization efficiency of the absorbed light.

Conventional surface texture treatment methods mainly employ chemical wet etching and dry etching using plasma. The dry etching method using plasma can be reproducible while achieving minimal etching, thereby increasing mass production. Possible equipment R & D is in progress, but because of the high cost of plasma etching equipment, there is a problem that the initial investment costs rise, making it difficult to adopt.

Recently, a technique has been developed in which polycrystalline silicon has a difficult surface organization by a chemical method and forms a groove using a laser, or a pyramid using a multi-faceted diamond blade. This method uses diamond blades to mechanically organize the surface and then remove surface defects with a chemical solution to form a regular pyramid with an angle of inclination of about 35 degrees.

However, since this method is a method of applying pressure mechanically using a diamond blade, as the thickness of the silicon substrate becomes thinner, there is a problem of increasing mechanical damage and inferior reproducibility.

The method using the laser has a problem that the investment in mass production facilities increases due to the high price of the laser equipment, and has a problem that the limitation of throughput, which is a fundamental problem of the treatment method by laser work, cannot be solved.

However, wet chemical etching, which is a method of etching a substrate using a chemical solution, is the most commercial method for surface organization of a silicon substrate for manufacturing a solar cell because of the lowest cost.

In order to surface-structure a silicon substrate by using such a wet chemical etching method, the surface of the silicon substrate is etched with a basic solution such as KOH or NaOH by using properties having different etching rates according to the crystal direction of the silicon substrate. Method was used.

That is, a basic solution such as KOH or NaOH having a concentration of 7% or more is heated to a temperature of 70 ° C. or higher to remove surface damage generated in the process of preparing a silicon substrate for solar cell, and 20 μm (front 10 μm, rear 10 μm) is removed. Remove

In order to form the surface of the silicon substrate, that is, to form a pyramid surface structure, the pyramid becomes about 10 μm by 20 minutes using 2% KOH IPA (2-isopropyl-alcohol) at a temperature of 85 to 90 ° C. Should be.

In this process of forming a pyramid surface structure, an additional 20 μm (front 10 μm, rear 10 μm) is removed.

Therefore, the thickness of 20 μm in the surface damage removal process, 20 μm in the surface texture process, and about 40 μm in total is lost.

As such, the thickness of the silicon substrate for solar cells using the wet chemical etching method is too large to lose the thickness of the solar cell in the process of increasing the mechanical failure rate, so conventional thinning of the solar cell is limited, In general, since a silicon substrate having a thickness of about 350 μm has to be used, there is a limit in lowering the production cost.

In addition, the pyramid surface organization method using a basic solution such as KOH or NaOH, as well as the problems caused by the etching process of the excessive thickness as described above, because the etching process using a different etching rate depending on the crystal direction of the silicon substrate different crystals There is a problem that a different approach is required for the surface organization of the oriented polycrystalline silicon substrate.

On the other hand, in order to separate the p-n junction by using a plasma etching, sandblasting etching, laser etching to remove the side of the silicon was separated.

That is, as shown in FIG. 1, in the p-n bonding process, n-type silicon 5 is formed on the upper and lower surfaces as well as the side surfaces of the p-type silicon 3 (see FIG. 1A). Accordingly, as shown in FIG. 1B by removing the n-type silicon 5 formed on the side surface, the n-type silicon 5a and 5b should be left only on the upper and lower surfaces of the p-type silicon 3. An etching method such as the above was used.

Then, while maintaining the n-type silicon (5b) layer formed on the rear surface as it is, by applying an aluminum electrode to all parts of the rear surface and heat treatment at a high temperature, aluminum is diffused to all areas of the rear surface to make a p ⁺ layer to make a rear electric field A technique for forming a back surface field was used.

Therefore, since the metal electrode is formed on the entire rear surface, the amount of metal required for the electrode increases, which causes a problem in that productivity is lowered.

An object of the present invention is to solve the problems of the prior art as described above, the thickness of the silicon substrate used to minimize the thickness to be etched for the surface organization, and the electrode required by locally forming the rear metal electrode It is to provide a porous silicon solar cell using a thin silicon substrate to increase the productivity of the solar cell by reducing the amount of metal and its manufacturing method.

In addition, the present invention has a secondary object to increase the photo-electric energy conversion efficiency by reducing the density of defects by the porous treatment of the portion other than the metal electrode formed locally on the back surface of the p-type silicon to enable baking at low temperature. .

In addition, the present invention is another object to increase the reliability by locally forming a metal electrode on the back surface of the p-type silicon, to prevent deformation in the metal electrode direction during the firing process.

The present invention to achieve the above object, (a) preparing a crystalline p-type silicon substrate; (b) forming a front porous silicon layer by porous treating the entire surface of the p-type silicon substrate; (c) forming an n-type silicon emitter layer on the entire surface of the front porous silicon layer; (d) forming a back porous silicon layer by porous treating the back surface of the p-type silicon substrate; (e) forming an anti-reflection film layer on the entire surface of the n-type silicon emitter layer; (f) locally forming front and rear metal electrodes on the front surface of the anti-reflection film layer and the rear surface of the rear porous silicon layer, respectively; (g) forming a porous silicon oxide layer by heat-treating the front or rear metal electrode and simultaneously oxidizing the remaining portion of the rear porous silicon layer in which the rear metal electrode is not formed; And (h) forming a back field effect layer on the back side of the p-type silicon substrate in contact with the back metal electrode by firing to provide a method of manufacturing a porous silicon solar cell using a thin silicon substrate. .

The p-type silicon substrate is a single crystal or polycrystalline silicon substrate, and a silicon substrate having a thickness of 240 μm or less.

The porous treatment of step (b) or (d) is performed by a wet chemical etching method, and the front porous silicon layer or the back porous silicon layer is oxidized by an acidic solution and an oxide film removed by hydrofluoric acid at the same time. Is formed.

The front porous silicon layer or the back porous silicon layer controls the ratio of the acidic solution and the hydrofluoric acid solution so that the oxide film is removed as soon as the oxide film is formed.

The acidic solution is nitric acid, and further includes water as a diluent, and the front porous silicon layer is formed by a solution in which the ratio of nitric acid: hydrofluoric acid: water is 18:15:11.

The rear porous silicon layer is made of a mixed solution such that the ratio of nitric acid: hydrofluoric acid: water is 2: 15: 5.

In step (b) or step (d), a gas exhaust treatment for exhausting the nitric oxide gas produced by the nitric acid component is simultaneously performed.

In step (b) or step (d), a cooling treatment for cooling the heat generated during the porous treatment is simultaneously performed.

The front porous silicon layer has a porosity of 65 to 75%, and the back porous silicon layer has a porosity of 45 to 55%.

In the step (c), the phosphoric acid solution (H ₃ PO ₄ ) is applied to the entire surface of the front porous silicon layer, and then heat-treated to form an n-type silicon emitter layer.

The phosphoric acid solution is applied by a spray method, and the phosphoric acid solution is diluted to 7 to 30% with respect to distilled water.

The heat treatment is carried out for 10 minutes at 900 ℃ using a furnace.

Step (c) further includes removing an oxide film formed during the diffusion treatment by the heat treatment, and the oxide film is removed by hydrofluoric acid.

The anti-reflection film layer of step (e) is made of a silicon nitride film, the silicon nitride film has a refractive index of 2.1 to 2.2 and a thickness of 65 to 75 nm.

The front metal electrode of step (f) is formed of 5 to 8% of the total area of the anti-reflection film layer using silver (Ag), and the back metal electrode of step (f) is made of aluminum Using Al or 3% Al / Ag, the area is 0.5 to 5% of the total area of the rear porous silicon layer, and the front or rear metal electrode is formed by screen printing.

The heat treatment of step (g) is performed for 5 minutes at 300 ℃ in the air, and the firing process of (h) is carried out for 1 second at 850 ℃.

And, the present invention is a p-type silicon substrate; A front porous silicon layer formed on the front surface of the p-type silicon substrate; An n-type silicon emitter layer formed on the front surface of the front porous silicon layer; An anti-reflection film layer formed on the entire surface of the n-type silicon emitter layer; A front metal electrode formed locally on the front surface of the anti-reflection film layer; A porous silicon oxide layer formed on a rear surface of the p-type silicon substrate; A rear metal electrode formed locally on the rear of the porous silicon oxide layer; And it provides a porous silicon solar cell using a thin silicon substrate comprising a back field effect layer formed between the porous silicon oxide layer and the back metal electrode.

The p-type silicon substrate is a single crystal or polycrystalline silicon substrate.

The porosity of the front porous silicon layer or the porous silicon oxide layer is 65 to 75% and 45 to 55%, respectively.

The front metal electrode is formed of silver (Ag), and has an area of 5 to 8% of the total area of the anti-reflection film layer, and the rear metal electrode is made of aluminum (Al) or 3% Al / Ag. It is formed with an area of 0.5 to 5% of the total area of the backside silicon oxide layer.

In addition, the present invention is a solar cell manufacturing method using a crystalline silicon substrate, in order to form a surface for light absorption, the front surface of the silicon substrate by etching the chemical wet etching method to form the pores in the depth direction of the thin silicon substrate It provides a method of manufacturing a porous silicon solar cell using.

The chemical wet etching is performed by removing an oxide film formed by oxidation and oxidation.

(Example)

A porous silicon solar cell using a thin silicon substrate according to the present invention and a method of manufacturing the same will be described with reference to the accompanying drawings.

The method of manufacturing a porous silicon solar cell using the thin silicon substrate according to the present invention will be described with reference to FIG. 2 and FIG.

1. p-type silicon substrate preparation

First, a single crystal or polycrystalline p-type silicon substrate 500 is prepared (S 10).

At this time, the p-type silicon substrate 500 uses a thickness of 240㎛ or less.

2. Formation of Front Porous Silicon Layer

In addition, in order to organize the surface of the p-type silicon substrate 500 having a thickness of 240 μm or less, in the present invention, a wet chemical etching method is used, using a chemical solution in which nitric acid, hydrofluoric acid, and water are mixed. The front porous silicon layer 400 is formed on the front surface of the 500 (S 11).

That is, pores are formed in the depth direction on the entire surface of the p-type silicon substrate 500 by using an oxide film formed by the nitric acid solution and an oxide film removed by the hydrofluoric acid solution. Here, the oxide film formation rate and the oxide film removal rate are made by adjusting the concentration of nitric acid or hydrofluoric acid of the chemical solution to the composition ratio region as shown in FIG. 6, wherein the front porous silicon layer 400 of the present invention is shown in FIG. A chemical solution consisting of the composition of zone 1 is used.

At this time, the shape of the p-type silicon substrate 500 according to the porosity of the pore is formed differently depending on the degree of porosity, as shown in FIG.

As shown in FIGS. 3C and 5, the porosity of the front porous silicon layer 400 formed on the entire surface of the p-type silicon substrate 500 is large, and the incident light flows out to the outside. It is preferably formed at 65 to 75%.

Here, referring to FIGS. 3 and 4A to 4C, the change in porosity, that is, the degree of organization of the surface according to each etching degree will be described below.

3 (A) corresponds to the initial stage of the etching process for the silicon surface in the case of the porosity of 10 to 25%, Figure 3 (B) is an etching treatment of the silicon surface in the case of 30 to 55% of the porosity. It is mid-term. 3 (C) corresponds to the completion stage during the etching process on the silicon surface when the porosity is 65 to 85%.

The etching of the silicon substrate is performed based on an arbitrary point at which the oxidizing action of the nitrate solution occurs first. At the same time, the oxidizing action is simultaneously performed on the surface of the silicon substrate. The etching proceeds by hydrofluoric acid.

In the present invention, nitric acid (HNO ₃ ): hydrofluoric acid (HF): water (H ₂ ) constituting a chemical solution used to form a front porous silicon layer 400 by porous treatment of the entire surface of the p-type silicon substrate 500. O) The composition ratio region of distilled water is shown in FIG. 6.

Area 1 of FIG. 6 is used to form the front porous silicon layer 400 on the surface of the p-type silicon substrate 500, that is, when the porosity of the front porous silicon layer 400 is 65 to 75%. A composition ratio region of the chemical solution, and region 2 is a chemical solution for forming pores at a porosity of 45 to 55% in the porous silicon oxide layer 600 formed on the back surface of the p-type silicon substrate 500, which will be described below. It is a composition ratio area.

The region 1 is a condition for forming pores at high porosity in order to reduce the reflectance since sunlight is incident on the front surface of the solar cell, and the region 2 is to form pores at low porosity in order to reduce recombination loss at the back of the solar cell. It is a condition for.

In the method of controlling the etching degree, as shown in regions 1 and 2 shown in FIG. 6, the front porous silicon layer 400 has a constant concentration of nitric acid (HNO ₃ ) and hydrofluoric acid (HF). In order to form pores while adjusting the porosity in the porous silicon oxide layer 600, the temperature of the chemical solution is adjusted in the range of 25 ° C to 10 ° C, or the porosity is controlled by reducing the etching time. On the contrary, the porosity is controlled by adjusting the temperature rise rate of the chemical solution in the range of 10 ° C to 25 ° C or by increasing the etching time.

In the initial stage of the etching process, the depth to be etched is low and the width of the pores is narrow. As the etching process time increases, the depth of the pores 11a to 11c etched in the silicon bodies 10a to 10c increases and the width thereof is increased. As it widens, the porosity increases.

4A to 4C show electron micrographs of the actual porous silicon surface according to the porosity of the porous silicon described with reference to FIG. 3. FIG. 4A shows the porosity of about 10% as a result of the electron microscopic examination of the porous silicon surface. 4b illustrates a case where the porosity of the porous silicon surface is about 30%, and FIG. 4c illustrates a case where the porosity of the porous silicon surface reaches about 70%.

The purpose of forming the pores on the surface of the silicon as described above is to reduce the reflectance of the sunlight incident on the front surface of the solar cell, and improve the length of the pass by using the internal reflection of the light, thereby increasing the amount of sunlight absorbed The purpose of the present invention is to improve photoelectric conversion efficiency by improving light utilization efficiency.

In other words, the size and angle of formation play an important role in the direction of light when the regular surface tissue structure is repeated two-dimensionally.

That is, in the angle of the surface structure and the reflection path of the light, if the surface structure has a path where the light is reflected twice only at the bottom of the V-shaped groove in which the surface texture is formed at a slope of 30 degrees, the slope of the surface texture At 45 degrees, all incident light is reflected twice, and at the bottom of the V-shaped groove having 54 degrees of inclination of the surface texture, light is reflected three times. It has a path in which incident light is reflected three times.

In the front porous silicon layer 400 formed as described above, since the pores 410 are formed in the depth direction with respect to the silicon body 420, the number of times of reflection of light incident into the pores 410 is reduced. Compared to the structure formed by the grooves in the shape of a child, the current generated by the light increases by that amount.

In the solar cell, since photoelectric conversion is mainly performed in a light ray region having a wavelength of 300 to 1200 nm, the front porous silicon 400 preferably has a thickness of 3,000 to 10,000 nm.

On the other hand, the wet chemical etching process for forming the front porous silicon layer 400 is heat and nitric oxide gas is generated during the chemical reaction, so it needs a cold treatment and exhaust treatment to cool it.

In addition, the surface reflectivity measurement results according to the porosity change of the front porous silicon layer 400 is shown in FIG. That is, in the case where the surface porosity, which is the ratio of pores 410 to the silicon body 420, is 20%, the surface reflectivity is 34% in the range of 300-1,200 nm light region, and when the porosity reaches 50% The average surface reflectivity is 11%, which is similar to the case of surface organization by alkaline with KOH or NaOH. When the porosity reaches 70%, the surface reflectivity decreases to about 5%, which is the lowest. After further etching, the surface reflectivity increases again. Therefore, in the present invention, it may be used to form pores in the porosity of 55 to 80% on the front porous silicon surface 400, but preferably formed in a porosity of 65 to 75%.

3. Form n-type Silicon Emitter Layer

After the front porous silicon layer 400 is formed as described above, an n-type silicon emitter layer 300 is formed on the front surface of the front porous silicon layer 400 to make a p-n junction structure (S 12).

The n-type silicon emitter layer 300 is formed by spraying a phosphoric acid solution (H ₂ PO ₄ ) diluted in distilled water to 7 to 30% in distilled water on the front surface of the front porous silicon layer 400 by using a furnace ( furnace for 10 minutes at a temperature of 860 ℃.

At this time, the oxide film (PSG) formed during the heat treatment process to diffuse the phosphorus (P) component added to convert the p-type silicon of the front porous silicon layer 400 to n-type silicon using 10% hydrofluoric acid It is removed by etching for 20 seconds, washed with pure water and dried.

4. Back Porous Silicon Layer Formation

The p-n junction is separated by forming a back porous silicon layer by performing a porous process on the back surface of the p-type silicon substrate 500 in a similar manner to the method of forming the front porous silicon layer 400 (S 13).

That is, in order to separate the pn junction, the pn junction portion formed on the side surface is removed by using one of several etching methods such as plasma etching, sandblasting etching, and laser etching. The back surface of the p-type silicon substrate 500 is formed by forming a back-side porous silicon layer in a similar manner to the formation of the front porous silicon layer 400 of the n-type silicon emitter layer 300 and the p-type silicon substrate 500 Pn junction edge isolation is achieved which electrically insulates the backside.

At this time, the porosity of the pores formed in the back porous silicon layer, as mentioned in the description of the front porous silicon layer 400, is formed in the range of 45 ~ 55%.

That is, in the back porous silicon layer, pores 610 are formed in a depth direction with respect to the silicon body 620 by a chemical solution formed as shown in region 2 of FIG. 6, and etching is performed first to form the pores ( 610 and the silicon body 620 which is etched slowly to form a flat surface, forming a porosity in the range of 45 to 55%, which is a condition for reducing recombination loss at the solar cell rear surface.

5. Anti-reflection film layer formation

An anti-reflection film layer 200 made of silicon nitride (SiN _x ) is formed on the entire surface of the n-type silicon emitter layer 300 to prevent reflection of sunlight and to reduce surface defect density (S 14).

The anti-reflection film layer 200 is a silicon nitride film containing hydrogen, and is widely used in solar cell fabrication because it serves to form the anti-reflection film layer 200 and surface / bulk passivation in a single process.

In this case, the chemical, mechanical, optical, electrical properties and passivation effects of the silicon nitride film vary according to the deposition method of the silicon nitride film used as the anti-reflection film layer 200. Therefore, in the present invention, the monosilane (SiH ₄ ), ammonia (NH ₃ ), and nitrogen (N ₂ ) or argon (Ar) gas are deposited by plasma-excited chemical vapor deposition (PECVD), which is suitable for the antireflection function. A silicon nitride film having a refractive index of 2.1 to 2.2 and a thickness of 65 to 75 nm was formed.

6. Formation of front / back metal electrode

The front metal electrode 100 and the rear metal electrode 700 are formed on the front surface of the anti-reflection film layer 200 and the rear surface of the rear porous silicon layer, respectively, at a local area (S 15).

The front metal electrode 100 is screen-printed silver (Ag) to the front of the anti-reflection film layer 200 in the range of 5 to 8% of the total area, and the rear metal electrode 700 is formed of the rear porous silicon layer Screen-print aluminum (Al) or 3% aluminum / silver (3% Al / Ag) metal electrodes on the back surface within a range of 0.5-5% of the total area.

At this time, the thickness of the p-type silicon substrate 500 is 250 μm, and the aluminum electrode is applied to the metal electrode, in particular, the rear metal electrode 700 at a thickness of 15 μm, thereby forming a rear field effect layer. When firing at, a phenomenon of bending at least 2 mm toward the aluminum may occur and may be broken. In the present invention, as described above, the rear metal electrode 700 is locally coated with a line width of 30 to 100 μm.

The front metal electrode 100 or the rear metal electrode 700 is preferably a line type or net mesh type through screen printing.

7. Dry / porous silicon oxide layer formation of metal electrode

After screen printing the front metal electrode 100 and the back metal electrode 700 as described above, and heat-treated for 5 minutes at a temperature of 300 ℃ (S 16).

In this case, in the heat treatment process for drying, the rear porous silicon layer of 92 to 95% of other portions in which the rear metal electrode 700 is not formed is oxidized and converted into the porous silicon oxide layer 600.

However, since the front porous silicon layer 400 is protected by the anti-reflection film layer 200, there is no change in state.

8. Formation of back field effect layer

After the heat treatment for drying the front metal electrode 100 and the back metal electrode 700 as described above, by rapid heat treatment for 1 second at a temperature of 850 ℃ (Firing) (S 17).

When the firing process is performed as described above, a rear field effect layer 800 is locally formed on a front surface of the rear metal electrode 700, that is, a portion where the rear metal electrode 700 and the p-type silicon substrate 500 are in contact with each other. The solar cell is completed.

Solar cell according to the present invention completed through the above process as shown in Figure 7, based on the p-type silicon substrate 500 having a thickness of 250㎛, the front porous on the front surface of the p-type silicon substrate A silicon layer 400 is formed, an n-type silicon emitter layer 300 is formed on the entire surface of the front porous silicon layer 400, an anti-reflection film layer 200 on the front of the n-type silicon emitter layer, and The front metal electrode 100 is locally formed on the front surface of the anti-reflection film layer 200.

In addition, a porous silicon oxide layer 600 formed by oxidizing a rear porous silicon layer on a rear surface of the p-type silicon substrate 500 is formed, and a rear metal electrode 700 locally on a rear surface of the porous silicon oxide layer 600. ) Is formed, and a rear field effect layer 800 is formed between the porous silicon oxide layer 600 and the rear metal electrode 700.

In the case of a solar cell having a length of 125 mm and an area of 147 cm ² , the first and second embodiments have the photoelectric energy conversion efficiency as shown in Table 1 and FIG. 8. This was over 17%.

Here, the first embodiment and the second embodiment are heat treatment for drying the front metal electrode 100 and the back metal electrode 700, respectively, by rapid heat treatment for 1 second at a temperature of 850 ℃ as a first embodiment The solar cell achieved by firing and firing by rapid heat treatment for 1.5 seconds at a temperature of 830 ° C. was used.

division First embodiment Second embodiment Item unit Short circuit current density (J _SC ) mA / cm ² 35.95 34.8 Open Voltage (V _OC ) mV 614.8 609.9 Short circuit current (I _SC ) A 5.32 5.15 Output power (P _m ) W 2.51 2.52 Output voltage (V _m ) mV 522.64 519.92 Maximum output current (I _m ) A 4.80 4.85 Curve Factor (FF) 0.767 0.8028 Energy conversion efficiency (Eff) % 17.07 17.04 Series resistance (R _s ) mΩ 7 5 Parallel resistance (R _sh ) Ω 38.82 18.35

The solar cell according to the present invention made as described above has a thickness of 240 μm of a silicon substrate and is manufactured using 1/10 of the conventional back metal electrode consumption, without damaging the substrate due to heat treatment. Energy conversion efficiency is higher than 17%.

The present invention made as described above by the surface chemical treatment of the surface of the solar cell by the wet chemical etching method, while achieving the surface texture while removing the existing 1/10 thickness, the surface reflectivity can be 5% to 10% In addition, the uniform coating of phosphoric acid (H ₃ PO ₄ ) enables the formation of a uniform n-type silicon emitter and facilitates a continuous process, thereby allowing a uniform doping process in large quantities. In addition, it is possible to manufacture a solar cell having a high efficiency of photoelectric energy conversion efficiency.

In addition, the present invention forms a porous silicon oxide layer after forming a porous silicon oxide layer by using a wet chemical etching to form a porous silicon oxide layer, thereby easily separating the pn junction, and rapidly oxidizing the surface of the rear porous silicon layer at low temperature. It improves conversion efficiency by eliminating unbonded silicon defects on the surface to improve short circuit current and curve factor characteristics. In addition, the metal electrode is locally formed to reduce the consumption of the metal electrode material and prevent shape distortion due to heat treatment, thereby manufacturing a thin sheet solar cell, and the metal electrode is locally formed to provide an effect of increasing the open voltage.

Claims (12)

(a) preparing a crystalline p-type silicon substrate; (b) forming a front porous silicon layer by porous treating the entire surface of the p-type silicon substrate; (c) forming an n-type silicon emitter layer on the entire surface of the front porous silicon layer; (d) forming a back porous silicon layer by porous treating the back surface of the p-type silicon substrate; (e) forming an anti-reflection film layer on the entire surface of the n-type silicon emitter layer; (f) locally forming front and rear metal electrodes on the front surface of the anti-reflection film layer and the rear surface of the rear porous silicon layer, respectively; (g) forming a porous silicon oxide layer by heat-treating the front or rear metal electrode and simultaneously oxidizing the remaining portion of the rear porous silicon layer in which the rear metal electrode is not formed; And (h) forming a back field effect layer on a back surface of the p-type silicon substrate in contact with the back metal electrode by firing; Method for producing a porous silicon solar cell using a thin silicon substrate comprising a. The method of claim 1, wherein the p-type silicon substrate is a monocrystalline or polycrystalline silicon substrate. The method of manufacturing a porous silicon solar cell using a thin silicon substrate according to claim 1 or 2, wherein the p-type silicon substrate has a thickness of 240 µm or less. The method of claim 1, wherein the porous treatment of step (b) or (d) is performed by a wet chemical etching method. 5. The method of claim 4, wherein the wet chemical etching controls the porosity by adjusting the oxide film formation by the acidic solution and the removal rate of the oxide film by the hydrofluoric acid. 6. The method of claim 1, wherein the front porous silicon layer has a porosity of 65 to 75%, and the back porous silicon layer has a porosity of 45 to 55%. According to claim 1, wherein the n-type silicon emitter layer of the step (c) using a thin silicon substrate, characterized in that the heat treatment after applying a phosphate solution (H ₃ PO ₄ ) to the entire surface of the front porous silicon layer Method of manufacturing a porous silicon solar cell. p-type silicon substrate; A front porous silicon layer formed on the front surface of the p-type silicon substrate; An n-type silicon emitter layer formed on the front surface of the front porous silicon layer; An anti-reflection film layer formed on the entire surface of the n-type silicon emitter layer; A front metal electrode formed locally on the front surface of the anti-reflection film layer; A porous silicon oxide layer formed on a rear surface of the p-type silicon substrate; A rear metal electrode formed locally on the rear of the porous silicon oxide layer; And A back field effect layer formed between the porous silicon oxide layer and the back metal electrode; Porous silicon solar cell using a thin silicon substrate comprising a. 9. The porous silicon solar cell of claim 8, wherein the porosity of the front porous silicon layer or the porous silicon oxide layer is 65 to 75% and 45 to 55%, respectively. 9. The thin silicon substrate of claim 8, wherein the rear metal electrode is formed with an area of 0.5 to 5% of the total area of the rear silicon oxide layer using aluminum (Al) or 3% Al / Ag. Porous silicon solar cell using. In the solar cell manufacturing method using a crystalline silicon substrate, Method of manufacturing a porous silicon solar cell using a thin silicon substrate to form the pores in the depth direction by oxidizing the entire surface of the silicon substrate by the chemical wet etching method and removing the oxide film formed by the oxidation for surface organization for light absorption. . The method of claim 11, wherein the pores are formed at a porosity of 65 to 75% on the front surface of the silicon substrate and 45 to 55% on the back surface of the silicon substrate.

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