KR20240010127A - Silicon solar cells containing carbon nanotubes doped with natural acids and their manufacturing methods - Google Patents

Abstract

One embodiment of the present invention provides a silicon solar cell including carbon nanotubes doped with natural acid and a method for manufacturing the same. According to one embodiment of the present invention, a silicon solar cell containing carbon nanotubes doped with natural acid prevents environmental pollution occurring during the compound synthesis process and does not generate toxic substances by using organic acids that can be produced biologically. Therefore, it is harmless to the human body and has excellent electrical performance due to the low reactivity, anti-reflection, and passivation effects of natural products.

Description

Silicon solar cells containing carbon nanotubes doped with natural acids and their manufacturing methods}

The present invention relates to a silicon solar cell and a manufacturing method thereof, and more specifically, to a silicon solar cell including carbon nanotubes doped with natural acid and a manufacturing method thereof.

Recently, due to the depletion of existing fossil fuels such as oil, coal, and natural gas, environmental pollution, and global warming, interest in energy that can replace these resources is increasing. Among them, solar cells are attracting attention because they are a permanent energy source and do not cause environmental pollution.

Solar cells are devices that convert solar light energy into electrical energy using the characteristics of semiconductor pn junctions, and are recognized as an important energy source of the future. Among these, thin-film solar cells are mainly used as ground-based solar cells, and types include CuInSe ₂ -based solar cells, amorphous Si solar cells, and CdTe solar cells.

Meanwhile, conventional wafers for solar cells are shipped as is after cutting and cleaning a silicon single-crystal sealing ingot, so there is a lot of damage and defects on the surface, and even if the defect removal process is performed during solar cell manufacturing, the defects are completely intact. There were limits to removing .

Due to Carbon Nanotube (CNT)'s excellent mechanical, electrical, thermal and optical properties, research is being actively conducted for its application in transparent and flexible next-generation electronic devices such as transparent electrodes, transparent transistors, and transparent sensors.

At this time, a doping process is necessary to improve the electrical performance of the carbon nanotube (CNT).

This doping process mainly uses nitric acid or triflic acid (TFMS), but these two inorganic acids are highly reactive and toxic, making them difficult to handle and causing environmental problems.

Conventionally used inorganic acids are strong acids with negative pKa values and are highly reactive, making them highly toxic and corrosive, making them unsuitable for the stability of solar cells.

In addition, since environmental pollution is caused by toxic organic solvents and incidental by-products used in the expensive chemical synthesis process, many attempts have been made to replace these inorganic acids, but these also have problems of being inefficient or inappropriate.

Therefore, many challenges still remain to manufacture solar cells that are harmless to the human body, do not cause environmental problems, and have improved electrical performance.

Republic of Korea Patent Publication No. 2013-0109308

The technical problem to be achieved by the present invention is to provide a silicon solar cell containing carbon nanotubes doped with natural acid, which is characterized by using natural acid synthesized by natural living organisms in the doping process of carbon nanotubes, and a method for manufacturing the same.

The technical problem to be achieved by the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned can be clearly understood by those skilled in the art from the description below. There will be.

In order to achieve the above technical problem, an embodiment of the present invention provides a silicon solar cell including carbon nanotubes doped with natural acid.

A silicon solar cell containing carbon nanotubes doped with the natural acid according to an embodiment of the present invention,

rear electrode layer;

A silicon layer made of n-type silicon located on top of the back electrode layer; And

The silicon layer is doped with natural acid and may include an electrode layer made of carbon nanotubes.

Additionally, according to an embodiment of the present invention, the back electrode layer may be made of platinum, titanium, silver, nickel, tin, or zinc metal.

Additionally, according to one embodiment of the present invention, the silicon layer may have a thickness of 100 μm to 500 μm.

Additionally, according to an embodiment of the present invention, in the carbon nanotube layer, the natural acid may be composed of formic acid, acetic acid, lactic acid, or citric acid.

Additionally, according to an embodiment of the present invention, in the carbon nanotube layer, the natural acid may be a p-type dopant.

Additionally, according to an embodiment of the present invention, in the carbon nanotube layer, the concentration of the natural acid may be 5% (w/w) to 50% (w/w).

Additionally, according to an embodiment of the present invention, in the carbon nanotube layer, the reflectance of the natural acid may be 5% to 30% or less.

In order to achieve the above technical problem, another embodiment of the present invention provides a method for manufacturing a silicon solar cell including carbon nanotubes doped with natural acid.

A method for manufacturing a silicon solar cell including carbon nanotubes doped with the natural acid according to an embodiment of the present invention,

Forming a back electrode layer on the back of a silicon layer composed of an n-type silicon substrate;

forming an electrode layer made of carbon nanotubes on the entire surface of the silicon layer; and

It may include doping natural acid onto the electrode layer composed of carbon nanotubes.

Additionally, according to an embodiment of the present invention, the back electrode layer may be made of platinum, titanium, silver, nickel, tin, or zinc metal.

Additionally, according to one embodiment of the present invention, the natural acid may be composed of formic acid, acetic acid, lactic acid, or citric acid.

Additionally, according to an embodiment of the present invention, the natural acid may be a p-type dopant.

A silicon solar cell containing carbon nanotubes doped with natural acid according to an embodiment of the present invention can remove all elements that cause environmental pollution generated during the compound synthesis process by using organic acids that can be produced biologically.

In addition, unlike inorganic acids, it does not produce toxic substances, and due to its low reactivity and high boiling point, it remains on the surface and has an anti-reflection effect. At the same time, it retains light due to the passivation effect caused by carboxylic acid. It has the effect of providing additional energy benefits.

The effects of the present invention are not limited to the effects described above, and should be understood to include all effects that can be inferred from the configuration of the invention described in the detailed description or claims of the present invention.

Figure 1 is a schematic diagram showing a silicon solar cell containing carbon nanotubes doped with natural acid.
Figure 2 shows the Raman spectroscopy results of CNTs doped with low and high concentrations of natural acid.
Figure 3 is a graph showing the results of XPS analysis of lactic acid and nitric acid.
Figure 4 is a graph showing the rate of change in resistance value of naturally doped CNTs over time.
Figure 5 is a reflectance graph of naturally doped CNT.
Figure 6 is the result of a finite difference time domain simulation to derive the optimal thickness of natural product.
Figure 7 is a FTIR graph measured when natural acids (a. acetic acid, b. lactic acid) were doped on a Si wafer or KBr pellet substrate.
Figure 8 is a FTIR graph measured when natural acids (c. formic acid, d. citric acid) were doped on a Si wafer or KBr pellet substrate.
Figure 9 is a QSSPC graph of each natural acid (a. acetic acid, b. formic acid, c. citric acid, d. lactic acid) or bare Si substrate.

Hereinafter, the present invention will be described with reference to the attached drawings. However, the present invention may be implemented in various different forms and, therefore, is not limited to the embodiments described herein. In order to clearly explain the present invention in the drawings, parts that are not related to the description are omitted, and similar parts are given similar reference numerals throughout the specification.

Throughout the specification, when a part is said to be "connected (connected, contacted, combined)" with another part, this means not only "directly connected" but also "indirectly connected" with another member in between. "Includes cases where it is. In addition, when a part is said to “include” a certain component, this does not mean that other components are excluded, but that other components can be added, unless specifically stated to the contrary.

The terms used herein are only used to describe specific embodiments and are not intended to limit the invention. Singular expressions include plural expressions unless the context clearly dictates otherwise. In this specification, terms such as “comprise” or “have” are intended to indicate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings.

A silicon solar cell including carbon nanotubes doped with natural acid according to an embodiment of the present invention will be described.

Figure 1 is a schematic diagram showing a silicon solar cell containing carbon nanotubes doped with natural acid.

Referring to Figure 1, a silicon solar cell including doped carbon nanotubes according to an embodiment of the present invention,

Back electrode layer (100); A silicon layer 200 made of n-type silicon located on the back electrode layer; and an electrode layer 300 doped with natural acid 400 on the silicon layer 200 and made of carbon nanotubes.

In addition, the present invention may further include a front electrode layer (gold, silver, copper, platinum, titanium) in which front electrodes are disposed spaced apart on an electrode layer composed of carbon nanotubes doped with natural acid on the silicon layer.

A silicon solar cell containing doped carbon nanotubes according to an embodiment of the present invention may include a back electrode layer 100.

At this time, the back electrode layer 100 may be made of platinum, titanium, silver, nickel, tin, or zinc metal, but is not limited to the metals mentioned above.

A silicon solar cell including doped carbon nanotubes according to an embodiment of the present invention may include a silicon layer 200.

The silicon layer 200 may be composed of n-type silicon.

The n-type silicon may contain one type selected from periodic elements of groups 13, 14, and 15, and is not limited to the above-mentioned examples, and any n-type semiconductor material is sufficient.

At this time, the thickness of the silicon layer 200 may be 100 μm to 500 μm, and the reason for setting the thickness to 100 μm to 500 μm is because it is the thickness that shows the highest efficiency in the process.

A silicon solar cell including doped carbon nanotubes according to an embodiment of the present invention may include electrode layers 300 and 400.

Carbon nanotubes are rolled graphene and are in the form of hollow tubes. Electrical characteristics vary depending on the direction in which it is rolled and the number of walls, and it periodically exhibits semiconductor or metallic properties. The carbon nanotubes have excellent mechanical, electrical, and thermal properties, so they can be applied in many fields, and can be synthesized by thermal chemical vapor deposition.

The carbon nanotubes rarely cause side reactions and do not corrode under oxygen conditions, allowing the photoelectric conversion efficiency of the solar cell to be maintained.

In the present invention, the carbon nanotube layer can be doped by coating formic acid, acetic acid, lactic acid, or citric acid as the natural acid 400.

At this time, the natural acid may refer to an acidic substance synthesized by living organisms through a biosynthesis process.

At this time, natural acids have a high boiling point characteristic, and the high boiling point characteristic is caused by hydrogen bonding being induced by having functional groups of the alcohol, amine, and sulfuric acid series and derivatives of the corresponding functional groups among acidic substances synthesized by living organisms. It may mean an increasing characteristic.

In addition, natural acids have passivation properties, and the passivation properties are due to the fact that among acidic substances synthesized by living organisms, alcohol, amine, sulfuric acid, carboxylic acid, and amide series functional groups and derivatives of the corresponding functional groups are capable of preventing defects on the crystal surface. It may refer to the characteristic of forming a complex.

At this time, the doping process of the natural acid can refer to any process that improves electrical properties by directly or indirectly contacting the natural acid with carbon nanotubes. In the present invention, a method of coating natural acid on carbon nanotubes was applied.

At this time, the natural acid 400 can serve as a p-type dopant, and the p-type dopant is an impurity additive added to the intrinsic semiconductor and does not generate electrons in the conduction band but creates holes in the valance band, thereby forming a p-type semiconductor. so that it can be formed.

The organic acids (formic acid, acetic acid, lactic acid, or citric acid) used in the present invention can be obtained from the animal and plant kingdom, and although organic acids have lower reactivity with metals than inorganic acids, they can achieve a relatively safe doping effect without damaging the metal.

In addition, when using organic acids, since they can be produced biologically in the animal and plant systems, the use of inorganic acids such as nitric acid or triflic acid can cause environmental pollution occurring during the synthesis of compounds, which is a problem in the prior art, and toxicity and corrosiveness due to strong acids. All problems caused by it can be eliminated.

In other words, the natural acid has a pKa value capable of doping carbon nanotubes and at the same time has the effect of not producing toxic substances, unlike conventionally used inorganic acids.

In addition, due to the low reactivity and high boiling point of natural acid, when the natural acid remains on the surface of the carbon nanotube, it can exhibit an anti-reflection effect, and due to the passivation effect by carboxylic acid. Since defects can be controlled, there can be an optical energy gain that increases photoelectric efficiency.

For example, the present invention is a method of forming a carbon nanotube layer, which involves dry transferring a SWNT (single walled nanotube) film to a silicon layer made of n-type silicon with a size of 3 mm × 3 mm and a peripheral electrode. ; It may include coating a natural acid on the SWNT film using a spin coating method.

In the present invention, the natural acid doped onto carbon nanotubes can be used by diluting it in distilled water, and the concentration of the natural acid may be 5% (w/w) to 50% (w/w).

At this time, the reason why the concentration of the natural acid is 5% (w/w) to 50% (w/w) is that there may be a problem that the doping effect is not visible when the concentration is lower than 5% (w/w), and 50% (w/w) This is because if the concentration is higher than the w/w) concentration, there may be a problem of deterioration of electrical properties due to organic acids.

In addition, in the present invention, the reflectance of natural acid may be 5% to 30% or less, and since the reflectance is 5% to 30% or less, silicon solar cells containing carbon nanotubes doped with natural acid improve performance by the light focusing effect. can be derived.

Additionally, a silicon solar cell including doped carbon nanotubes according to an embodiment of the present invention may further include a front electrode layer.

The front electrode layer may be made of platinum, titanium, silver, nickel, tin, or zinc metal, but may not be limited to the metals mentioned above.

At this time, the front electrode layer may be electrically connected to the electrode layer composed of carbon nanotubes doped with natural acid.

A silicon solar cell containing carbon nanotubes doped with natural acid according to an embodiment of the present invention uses natural acid as a p-type dopant and has a low pKa value, so unlike conventionally used inorganic acids, it does not generate toxic substances. However, due to its low reactivity and high boiling point, it can remain on the surface to prevent reflection, and has the effect of reducing defects through the passivation effect due to carboxylic acid.

Therefore, the silicon solar cell according to an embodiment of the present invention uses natural acid, which has the effect of showing a higher photoelectric efficiency of 10.3% than when using existing inorganic acid.

A method for manufacturing a silicon solar cell including carbon nanotubes doped with natural acid according to another embodiment of the present invention will be described.

A method for manufacturing a silicon solar cell including doped carbon nanotubes according to another embodiment of the present invention,

Forming a back electrode layer on the back of a silicon layer composed of an n-type silicon substrate; It may include forming an electrode layer made of carbon nanotubes on the entire surface of the silicon layer; and doping natural acid on the electrode layer made of carbon nanotubes.

In the first step, it may include forming a back electrode layer on the back of a silicon layer composed of an n-type silicon substrate.

The back electrode layer can be formed by drying with an N ₂ gun and then performing a sputtering process to make it composed of Ti (10 nm)/Pt (55 nm).

In the second step, it may include forming an electrode layer made of carbon nanotubes on the entire surface of the silicon layer.

To form the carbon nanotube layer, a carbon nanotube film can be produced.

At this time, the carbon nanotube film can be synthesized by an aerosol (suspended catalyst) CVD method based on ferrocene vapor decomposition in a carbon monoxide (CO) atmosphere.

The method of producing the carbon nanotube film includes vaporizing CO at room temperature by passing it through a cartridge filled with a catalyst precursor and ferrocene powder, and then introducing a flow containing ferrocene vapor into the high temperature region of the ceramic tube reactor through a water-cooled probe. and mixing with additional CO; mixing a controlled amount of CO ₂ with CO carbon to obtain stable growth of SWNTs; This may include collecting carbon nanotubes directly downstream of the reactor by filtering the flow through a nitrocellulose or silver membrane filter (Millipore Corp., USA; HAWP, 0.45 μm pore diameter).

In the present invention, the carbon nanotube film produced by the above-described process can be coated on the entire surface of the silicon layer by performing a dry-transfer method.

The method of coating the carbon nanotube film described above is an example, and spray coating and spin coating methods using a solution can be applied.

At this time, the carbon nanotube film may be coated to a thickness of 20 nm to 50 nm.

In the third step, it may include doping natural acid onto the electrode layer composed of carbon nanotubes.

At this time, the natural acid may be composed of formic acid, acetic acid, lactic acid, or citric acid.

The concentration of the natural acid may be 5% (w/w) to 50% (w/w).

At this time, the reason why the concentration of the natural acid is 5% (w/w) to 50% (w/w) is that there may be a problem that the doping effect is not visible when the concentration is lower than 5% (w/w), and 50% (w/w) This is because if the concentration is higher than the w/w) concentration, there may be a problem of deterioration of electrical properties due to organic acids.

Preparing a natural acid solution to dope the natural acid into the carbon nanotube layer; The step of coating the natural acid solution on the carbon nanotube layer may be performed.

The natural acid carboxylic acid functional group (-COOH) can fill the trap level on the silicon surface through a passivation effect.

The silicon surface filled with the trap level can improve photoelectric efficiency by improving carrier stability.

At this time, the step of forming a front electrode layer so that the upper electrodes are spaced apart from each other on the carbon nanotube layer doped with the natural acid may be further included.

At this time, the front electrode layer may be made of platinum, titanium, silver, nickel, tin, or zinc metal.

For example, as a method of forming the front electrode layer, a Ti (10 nm)/Pt (55 nm) front electrode can be formed by performing a sputtering process on the front surface of a substrate with a 3 mm × 3 mm physical mask array.

Therefore, the method for manufacturing a silicon solar cell including carbon nanotubes doped with natural acid according to an embodiment of the present invention can replace existing p-type silicon wafers and thus satisfy low cost, ease of use, and eco-friendliness.

Preparation Example 1: Preparation of a silicon solar cell containing carbon nanotubes doped with formic acid

First, the n-type Si substrate was heat treated with RCA1 (H ₂ O:NH ₄ OH:H ₂ O ₂ =5:1:1) at 70°C for 30 minutes to remove dust and organic matter on the substrate surface.

Next, the SiO ₂ layer on both sides of the n-type Si substrate was removed with 5 m NaOH for 20 minutes at approximately 95°C.

Next, the substrate on which the SiO ₂ layer was etched was taken out of the NaOH solution, quickly washed with RCA2 (H ₂ O:NH ₄ OH:H ₂ O ₂ =5:1:1) for 3 seconds, and then rinsed with distilled water.

Next, after drying with an N ₂ gun, a back electrode of Ti (10 nm)/Pt (55 nm) was sputtered on the back side of the substrate.

Next, after removing the physical mask, the SWNT film was transferred to the upper surface of the substrate using a dry-transfer method.

Next, ethanol was dropped on the transferred film to improve the contact performance between the SWNT film and the substrate.

Next, 5 to 50 ml of formic acid as a natural acid was diluted with 100 ml of distilled water.

Next, the diluted formic acid solution was spin-coated on the SWNT film of the SWNT-Si solar cell at 5000 rpm for 60 seconds.

Preparation Example 2: Preparation of a silicon solar cell containing carbon nanotubes doped with acetic acid

First, the n-type Si substrate was heat treated with RCA1 (H ₂ O:NH ₄ OH:H ₂ O ₂ =5:1:1) at 70°C for 30 minutes to remove dust and organic matter on the substrate surface.

Next, the SiO2 layer on both sides of the n-type Si substrate was removed with 5 m NaOH for 20 min at approximately 95°C.

Next, the substrate on which the SiO ₂ layer was etched was taken out of the NaOH solution, quickly washed with RCA2 (H ₂ O:HCl:H ₂ O ₂ =5:1:1) for 3 seconds, and then rinsed with distilled water.

Next, after drying with an N ₂ gun, a back electrode of Ti (10 nm)/Pt (55 nm) was sputtered on the back side of the substrate.

Next, after removing the physical mask, the SWNT film was transferred to the upper surface of the substrate using a dry-transfer method.

Next, ethanol was dropped on the transferred film to improve the contact performance between the SWNT film and the substrate.

Next, 5 to 50 ml of acetic acid as a natural acid was diluted with 100 ml of distilled water.

Next, the diluted acetic acid solution was spin-coated on the SWNT film of the SWNT-Si solar cell at 5000 rpm for 60 seconds.

Preparation Example 3: Preparation of a silicon solar cell containing carbon nanotubes doped with lactic acid

First, the n-type Si substrate was heat treated with RCA1 (H ₂ O:NH ₄ OH:H ₂ O ₂ =5:1:1) at 70°C for 30 minutes to remove dust and organic matter on the substrate surface.

Next, the SiO2 layer on both sides of the n-type Si substrate was removed with 5 m NaOH for 20 min at approximately 95°C.

Next, the substrate on which the SiO ₂ layer was etched was taken out of the NaOH solution, quickly washed with RCA2 (H ₂ O:HCl:H ₂ O ₂ =5:1:1) for 3 seconds, and then rinsed with distilled water.

Next, after drying with an N ₂ gun, a back electrode of Ti (10 nm)/Pt (55 nm) was sputtered on the back side of the substrate.

Next, after removing the physical mask, the SWNT film was transferred to the upper surface of the substrate using a dry-transfer method.

Next, ethanol was dropped on the transferred film to improve the contact performance between the SWNT film and the substrate.

Next, 5 to 50 ml of lactic acid as a natural acid was diluted with 100 ml of distilled water.

Next, the diluted lactic acid solution was spin-coated on the SWNT film of the SWNT-Si solar cell at 5000 rpm for 60 seconds.

Preparation Example 4: Preparation of a silicon solar cell containing carbon nanotubes doped with citric acid

First, the n-type Si substrate was heat treated with RCA1 (H ₂ O:NH ₄ OH:H ₂ O ₂ =5:1:1) at 70°C for 30 minutes to remove dust and organic matter on the substrate surface.

Next, the SiO2 layer on both sides of the n-type Si substrate was removed with 5 m NaOH for 20 min at approximately 95°C.

Next, the substrate on which the SiO2 layer was etched was taken out of the NaOH solution, quickly washed with RCA2 (H ₂ O:HCl:H ₂ O ₂ =5:1:1) for 3 seconds, and then rinsed with distilled water.

Next, after drying with an N ₂ gun, a back electrode of Ti (10 nm)/Pt (55 nm) was sputtered on the back side of the substrate.

Next, after removing the physical mask, the SWNT film was transferred to the upper surface of the substrate using a dry-transfer method.

Next, ethanol was dropped on the transferred film to improve the contact performance between the SWNT film and the substrate.

Next, 5 to 50 ml of citric acid as a natural acid was diluted with 100 ml of distilled water.

Next, the diluted citric acid solution was spin-coated on the SWNT film of the SWNT-Si solar cell at 5000 rpm for 60 seconds.

Experimental Example 1: Experiment to confirm the degree of CNT doping of natural products

Figure 2 shows the Raman spectroscopy results of CNTs doped with low and high concentrations of natural acid.

Figure 2 shows the G spectrum measured when (a) lactic acid, (b) formic acid, and (c) citric acid were applied to the CNT film and (d) lactic acid, (e) formic acid, and (f) citric acid were applied to the CNT film. In one case, it shows the measured 2D band spectrum.

In FIG. 2, the difference in conductivity can be shown in the case of the G band, and the degree of p-doping effect can be shown in the case of the 2D band.

Referring to FIG. 2, the Raman G bands of the lactic acid-doped CNT film (FIG. 2a), formic acid-doped CNT film (FIG. 2b), and citric acid-doped CNT film (FIG. 2c) are blue shifted, indicating that the Raman G bands are blue-shifted to lactic acid. , it can be confirmed that both formic acid and citric acid are p-type doped.

In addition, the Raman 2D bands of the lactic acid-doped CNT film (Figure 2c), formic acid-doped CNT film (Figure 2d), and citric acid-doped CNT film (Figure 2e) were blue shifted, indicating that lactic acid, formic acid, and citric acid were all You can confirm that it is p-type doped.

At this time, lactic acid can induce an antireflection effect due to its tendency to densify CNTs through a network with large hydrogen bonds and form a thin and uniform coating.

At this time, it can be confirmed that the doping effect is excellent when the citric acid concentration is high, as the G band and 2D band graphs are less blue shifted when the citric acid concentration is low compared to the high concentration.

On the other hand, it can be confirmed that lactic acid and formic acid showed a sufficiently strong doping effect at both high and low concentrations.

Therefore, it is preferable to use lactic acid or formic acid as the natural acid in the present invention, and more preferably lactic acid.

Figure 3 is a graph showing the results of XPS analysis of lactic acid and nitric acid.

Carbon and oxygen peaks in XPS shifting to lower binding energies may indicate that the Fermi level is approaching the valence band.

Therefore, referring to Figure 3(a), it can be confirmed that p-doping is observed as the value of the graph decreases from 284.2 eV of the general CNT electrode. Additionally, referring to Figure 3(b), it can be confirmed that the value of the graph is p-doping as the portion of the C=O peak generated by doping increases.

Experimental Example 2: Experiment to confirm doping stability of natural products

Figure 4 is a graph showing the rate of change in resistance value of naturally doped CNTs over time.

Referring to FIG. 4, it can be seen that the resistance value change rate does not change at 25%, so that the lactic acid-doped CNT film shows much greater stability than the formic acid-doped CNT film from the doping durability perspective.

The reason why the stability of lactic acid is greater is that lactic acid exhibits a weak doping effect due to the attached hydroxyl group that attracts electrons from the carboxyl group, which has the property of destabilizing the conjugate base. From the viewpoint of doping durability, the lactic acid-doped CNT film is better than the formic acid-doped CNT film. It shows much greater stability than CNT film, so the stability of lactic acid is superior.

Therefore, among lactic acid, formic acid, citric acid, and acetic acid, it is preferable to use lactic acid or formic acid as a natural acid in the present invention, and more preferably, lactic acid is used.

Experimental Example 3: Experiment to confirm the anti-reflection effect of natural products and experiment to confirm the optimal thickness of natural products

Figure 5 is a reflectance graph of naturally doped CNT.

Specifically, Figure 5 is a graph measuring reflectance (Reflectance%) according to the anti-reflection effect of a silicon solar cell containing CNT doped with natural acid.

Referring to Figure 5(a), the reflectance (Reflectance%) of the silicon solar cell including the CNT film doped with lactic acid decreases and then increases, while referring to Figure 5(b), the CNT film to which formic acid is applied. It can be seen that the reflectance has increased.

Therefore, through Figure 5, it can be seen that natural acids consisting of lactic acid and formic acid increase the reflectance, so lactic acid has a better anti-reflection effect.

At this time, a carbon nanotube film doped with highly concentrated lactic acid may exhibit a greater antireflection effect than a carbon nanotube film doped with low concentrated lactic acid.

Referring to FIG. 6, the optimal thickness was derived as a result of Si/CNT/lactic acid modeling using finite-difference time-domain (FDTD) simulation. As a result, it can be confirmed that 50 to 100 nm shows the best anti-reflection effect.

Experimental Example 4: Experiment to confirm the passivation effect of natural products

Figure 7 is a FTIR graph measured when natural acids (a. acetic acid, b. lactic acid) were doped on a Si wafer or KBr pellet substrate.

Referring to Figure 7 (a, b, c), the passivation effect of acetic acid can be confirmed by the disappearance of the O-H peak of the acetic acid-doped silicon wafer and the shift of the peaks of C-O, C=O, and C-H.

In addition, referring to Figure 7 (d, e, f), the passivation effect of lactic acid can be confirmed by the reduction of the O-H peak of the silicon wafer doped with lactic acid and the shift of the peaks of C-O, C=O, and C-H.

At this time, the lone pair of electrons in the carboxyl group in the lactic acid forms a Lewis coordination at the Si defect and can control the defect, thereby improving the photoelectric efficiency of the silicon solar cell.

Figure 8 is a FTIR graph measured when natural acids (c. formic acid, d. citric acid) were doped on a Si wafer or KBr pellet substrate.

Referring to Figure 8 (a, b, c), the passivation effect of formic acid can be confirmed by the reduction of the O-H peak of the formic acid-doped silicon wafer and the shift of the peaks of C-O, C=O, and C-H.

In addition, referring to Figure 8 (d, e, f), the passivation effect of lactic acid can be confirmed by the reduction of the O-H peak of the citric acid-doped silicon wafer and the shift of the peaks of C-O, C=O, and C-H.

Experimental Example 5: Experiment to confirm the improvement of charge carrier lifespan of natural products

Figure 9 is a QSSPC graph of each natural acid (a. acetic acid, b. formic acid, c. citric acid, d. lactic acid) or bare Si substrate.

QSSPC (quasi-steady-state photo-conductance) is a method of irradiating a strong light pulse to a semiconductor gas, generating photo-organic carriers such as electrons and holes in the semiconductor gas, and measuring the time decay rate of the generated photo-organic carriers. am. This method is widely used because it is simple.

As a result of confirming the correlation between lifetime and carrier density obtained through the QSSPC measurement, formic acid in Figure 9(b) and citric acid in Figure 9(c) have graph values compared to the pure silicon substrate in Figure 9(e). Considering that this is similar or slightly increased, it can be seen that the passivation characteristics are not significant.

It can be confirmed that the acetic acid in Figure 9(a) and the lactic acid in Figure 9(d) have good passivation characteristics as the graph values have increased significantly compared to the pure silicon substrate in Figure 9(e).

The description of the present invention described above is for illustrative purposes, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical idea or essential features of the present invention. will be. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. For example, each component described as unitary may be implemented in a distributed manner, and similarly, components described as distributed may also be implemented in a combined form.

The scope of the present invention is indicated by the patent claims described below, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention.

100: back electrode layer
200: Silicon layer
300: electrode layer
400: natural product

Claims (11)

rear electrode layer;
A silicon layer made of n-type silicon located on top of the back electrode layer; And
A silicon solar cell including carbon nanotubes doped with natural acid on the silicon layer and comprising an electrode layer made of carbon nanotubes. According to paragraph 1,
A silicon solar cell containing carbon nanotubes doped with natural acid, wherein the rear electrode layer is composed of platinum, titanium, silver, nickel, tin, or zinc metal. According to paragraph 1,
A silicon solar cell containing carbon nanotubes doped with natural acid, wherein the silicon layer has a thickness of 100 μm to 500 μm. According to paragraph 1,
In the carbon nanotube layer,
A silicon solar cell containing carbon nanotubes doped with a natural acid, wherein the natural acid consists of formic acid, acetic acid, lactic acid, or citric acid. According to paragraph 1,
In the carbon nanotube layer,
A silicon solar cell containing carbon nanotubes doped with natural acid, wherein the natural acid is a p-type dopant. According to paragraph 1,
In the carbon nanotube layer,
A silicon solar cell containing carbon nanotubes doped with natural acid, wherein the concentration of the natural acid is 5% (w/w) to 50% (w/w). According to paragraph 1,
In the carbon nanotube layer,
A silicon solar cell containing carbon nanotubes doped with natural acid, characterized in that the reflectance of the natural acid is 5% to 30% or less. Forming a back electrode layer on the back of a silicon layer composed of an n-type silicon substrate;
forming an electrode layer made of carbon nanotubes on the entire surface of the silicon layer; and
A method of manufacturing a silicon solar cell including carbon nanotubes doped with natural acid, comprising the step of doping natural acid on the electrode layer composed of carbon nanotubes. According to clause 8,
A method of manufacturing a silicon solar cell including carbon nanotubes doped with natural acid, wherein the back electrode layer is composed of platinum, titanium, silver, nickel, tin, or zinc metal. According to clause 8,
A method of manufacturing a silicon solar cell including carbon nanotubes doped with a natural acid, wherein the natural acid consists of formic acid, acetic acid, lactic acid, or citric acid. According to clause 8,
A method of manufacturing a silicon solar cell including carbon nanotubes doped with natural acid, wherein the natural acid is a p-type dopant.