KR20160001437A

KR20160001437A - Texturing method of solar cell surface

Info

Publication number: KR20160001437A
Application number: KR1020140079976A
Authority: KR
Inventors: 이재갑; 정대균; 이치영; 이택경
Original assignee: 국민대학교산학협력단
Priority date: 2014-06-27
Filing date: 2014-06-27
Publication date: 2016-01-06
Also published as: KR101652342B1

Abstract

The present invention provides a method for texturing the surface of a solar cell. The method for texturing the surface of a solar cell includes the following steps: applying a photoresist on a substrate; forming a pattern on the substrate by using a mold having repeated patterns, and curing the pattern; and etching the substrate. According to the present invention, the method patterns the photoresist on the substrate by using imprinting or lithography when texturing the surface of a solar cell. At this time, the method increases an area of a substrate surface exposing unit by using texturing, thereby decreasing reflectivity and increasing solar cell efficiency.

Description

{TEXTURING METHOD OF SOLAR CELL SURFACE}

The present invention relates to a method of texturing a solar cell surface.

A solar cell is a core element of solar power generation that converts sunlight directly into electricity. Basically, it is a diode made of p-n junction. When the sunlight is converted into electricity by the solar cell, solar light is incident on the pn junction of the solar cell, that is, the active layer, and electron-hole pairs are generated. The electrons move to the n layer by the electric field, p layer, and photovoltaic power is generated between the pn junctions. When a load or a system is connected to both ends of the solar cell at this time, a current flows and a power can be produced.

Such a solar cell is divided into various types according to the material and the form of the active layer. Typically, it is a silicon-based solar cell using a typical pn structure or a pin structure, a II-VI compound semiconductor of CdTe, CuInSe, CuInGeSe or GaAs, A compound semiconductor solar cell using a Group V compound semiconductor, a dye-sensitized solar cell in which a nanoparticle and a dye are combined and filled with an electrolyte solution or a solid electrolyte, and an organic solar cell using an organic polymer and a monomolecular material.

Such a solar cell maximizes the absorption of light by surface texturing the surface of the substrate as one method for increasing the efficiency. As the surface tacking method, wet etching, dry etching, mechanical polishing, photolithography and the like are used.

The wet etching method has been widely used because it can tackle a large number of wafers at a low cost for a short time. However, there is a problem that the surface is not uniformly tackled. To solve this problem, over etching can reduce the surface area, and the impact can accumulate and affect the rigidity of the substrate.

Korean Patent No. 0180621 discloses an etching solution for taxing comprising isopropyl alcohol. However, since the etching solution contains isopropyl alcohol having a low boiling point, it is not economical from the viewpoint of productivity and cost because it is required to add isopropyl alcohol during the taxing step, and the temperature gradient of the etching solution is caused by the added isopropyl alcohol The degree of tacking may vary depending on the position of the surface of the silicon wafer, and the uniformity may be deteriorated.

The present application provides a taxing method of a solar cell surface.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned can be clearly understood by those skilled in the art from the following description.

According to a first aspect of the present invention, there is provided a method of manufacturing a semiconductor device, comprising: applying a photoresist to a substrate; Forming a pattern on the substrate using a mold having a pattern of repeated structures, and then curing the pattern; And etching the substrate. The present invention also provides a method of tackling a solar cell surface.

According to the present invention, when tackling a surface of a solar cell, a photoresist is patterned on a substrate using imprinting, lithography, or the like. At this time, a plurality of patterns are formed by controlling the hole size of the pattern, the etching solution, the etching time and the like, and the area of the substrate surface exposed portion is increased by using taxation, thereby reducing the reflectivity and increasing the solar cell efficiency have.

In addition, by using a mold having a pattern of repeated structures including a hexagonal close-packed structure according to an embodiment of the present invention, overall taxing of the surface exposed portion occurs and pyramid-shaped microtasking is formed in the pattern, It is also possible to adjust the reflectivity.

1 is a flow chart illustrating a taxing process in one embodiment of the present application.
2 is a schematic view showing a pattern shape of a mold according to an embodiment of the present invention.
FIG. 3A is a planar SEM image of the substrate surface after the surface taxing process and FIG. 3B is a cross-sectional SEM image of the substrate surface after the surface taxing process, in one embodiment of the present invention.
FIG. 4A is a cross-sectional SEM image showing the size of the surface pattern when etching for about 2 minutes in the embodiment of the present invention, and FIG. 4B is a planar SEM image showing the size of microtasking when etching for about 2 minutes.
FIG. 5A is a cross-sectional SEM image showing the size of the surface pattern when etching for about 4 minutes and FIG. 5B is a planar SEM image showing the size of microtasking when etching for about 4 minutes in the embodiment of the present invention.
FIG. 6A is a cross-sectional SEM image showing the surface pattern size when etching for about 8 minutes and FIG. 6B is a planar SEM image showing the size of microtasking when etching for about 8 minutes in one embodiment of the present invention.
FIG. 7 is a graph showing the result of reducing the reflectance according to the etching time in the embodiment of the present invention. FIG.
FIG. 8 is a graph showing the result of reduction in reflectivity according to the etching time in one embodiment of the present invention. FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when a part is referred to as being "connected" to another part, it is not limited to a case where it is "directly connected," but also includes the case where it is "electrically connected" do.

Throughout this specification, when a member is " on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, when an element is referred to as " including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise. The terms " about ", " substantially ", etc. used to the extent that they are used throughout the specification are used to refer to the manufacturing and material tolerances inherent in the meanings mentioned, Accurate or absolute numbers are used to help prevent unauthorized exploitation by unauthorized intruders of the referenced disclosure. The word " step (or step) " or " step " used to the extent that it is used throughout the specification does not mean " step for.

Throughout this specification, the term " combination (s) thereof " included in the expression of the machine form means a mixture or combination of one or more elements selected from the group consisting of the constituents described in the expression of the form of a marker, Quot; means at least one selected from the group consisting of the above-mentioned elements.

Throughout this specification, the description of "A and / or B" means "A or B, or A and B".

Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to these embodiments and examples and drawings.

FIG. 1 is a flowchart illustrating a method of taxing a surface of a solar cell according to an embodiment of the present invention.

As shown in Fig. 1, a method of taxing a solar cell surface according to the present invention firstly comprises cleaning the substrate 10 according to a conventional method. For example, the substrate 10 may be cleaned using hydrogen fluoride, but it is not limited thereto.

According to one embodiment of the disclosure, the substrate 10 may be selected from the group consisting of single crystalline, micro crystalline, poly crystalline, amorphous, and combinations thereof. , But may not be limited thereto. The substrate 10 may be made of various materials or substrates having a crystal form regardless of the material or the shape, but may not be limited thereto.

Next, a photo resist (hereinafter also referred to as "PR") 20 is applied to the cleaned substrate 10. The application of the photoresist 20 may be performed by a method selected from the group consisting of spin coating, dipping coating, roll to roll coating, flow coating, spray coating, and combinations thereof, but is not limited thereto .

The mold 30 is brought into contact with the substrate 10 to which the photoresist 20 is applied.

According to one embodiment of the present invention, forming the pattern of the mold 30 on the substrate 10 may be accomplished by imprinting, lithography, gravure printing, roll-to-roll printing, and combinations thereof.

According to one embodiment of the present invention, the pattern of the repeated structure included in the mold 30 may include a hexagonal close-packed structure as shown in FIG. 2, but the present invention is not limited thereto. The mold having the pattern of the hexagonal close-packed structure includes a pattern portion of the hole performance pattern and a pattern portion of the even performance pattern in which the pattern is formed at regular intervals, and the pattern portion of the hole performance and the pattern portion of the even performance are spaced apart from each other, It means a mold that forms a pattern.

According to one embodiment of the disclosure, the pattern of the repeating structure may have a size of from about 100 nm to about 10 탆, but may not be limited thereto. For example, the size of the pattern can be from about 100 nm to about 10 urn, from about 100 nm to about 1 탆, from about 100 nm to about 900 nm, from about 100 nm to about 800 nm, from about 100 nm to about 700 nm, From about 100 nm to about 600 nm, from about 100 nm to about 600 nm, from about 100 nm to about 500 nm, from about 100 nm to about 400 nm, from about 100 nm to about 300 nm, or from about 100 nm to about 200 nm.

According to one embodiment of the present application, the pattern of the repeating structure may be, but not limited to, having an interval of about 1 [mu] m to about 100 [mu] m. For example, the spacing of the pattern may be from about 1 micrometer to about 100 micrometers, from about 1 micrometer to about 90 micrometers, from about 1 micrometer to about 80 micrometers, from about 1 micrometer to about 70 micrometers, from about 1 micrometer to about 60 micrometers, From about 1 micrometer to about 50 micrometers, from about 1 micrometer to about 40 micrometers, from about 1 micrometer to about 30 micrometers, from about 1 micrometer to about 20 micrometers, or from about 1 micrometer to about 10 micrometers.

In one embodiment of the invention, the use of the mold 30, which includes a size of between about 100 nm and about 10 microns and a spacing between patterns of between about 1 microns and about 100 microns, , Overall taxing of the surface exposed portion of the substrate 10 may occur.

Then, the substrate 10 is heat-treated. For example, the heat treatment may be performed by heating or ultraviolet irradiation, but the present invention is not limited thereto.

According to an embodiment of the present invention, after the substrate 10 is heat-treated, the mold 30 is detached and the remaining film of the photoresist 20 remaining in the pattern formed on the substrate 10 is removed But may not be limited thereto. For example, removing the residual film may be performed by a plasma, but may not be limited thereto.

Finally, the substrate 10 is etched.

According to one embodiment of the invention, etching the substrate 10 may be performed by a method selected from the group consisting of wet etching, dry etching, mechanical etching, and combinations thereof, but is not limited thereto .

According to one embodiment of the present application, the wet etching may be performed using a mixed solution selected from the group consisting of hydrogen fluoride, nitric acid, acetic acid, and combinations thereof, but may not be limited thereto.

According to one embodiment of the present application, the wet etching may be performed using a solution containing about 0.5% to about 5% by weight of the nitric acid with respect to about 100% by weight of the hydrogen fluoride, . For example, the nitric acid may be present in an amount ranging from about 0.5 wt% to about 5 wt%, from about 0.5 wt% to about 4 wt%, from about 0.5 wt% to about 3 wt%, from about 0.5 wt% % To about 2 wt%, or about 0.5 wt% to about 1 wt%, based on the total weight of the composition. For example, when a solution containing the above range is used, a rough surface can be obtained, thereby reducing the reflectivity on the surface of the solar cell. For example, when a solution out of the above range is used, a rough surface can not be obtained, and a reduction in reflectivity can not also be obtained. If the amount of nitric acid is less than about 0.5 wt%, a uniform etching surface can not be obtained due to a high etching rate, and if the nitric acid exceeds about 5 wt%, the occurrence of surface defects is increased due to a low etching rate, The efficiency of the battery can be reduced.

According to one embodiment of the present application, the wet etching may be performed using a solution containing about 1% to about 10% by weight of the acetic acid with respect to about 100% by weight of the hydrogen fluoride, . For example, for about 100 wt% of the hydrogen fluoride, the acetic acid may be present in an amount ranging from about 1 wt% to about 10 wt%, from about 1 wt% to about 9 wt%, from about 1 wt% to about 8 wt% From about 1% to about 3%, or from about 1% to about 5%, from about 1% to about 5%, from about 1% To about 2% by weight, based on the total weight of the composition. For example, when a solution containing the above range is used, a rough surface can be obtained, thereby reducing the reflectivity on the surface of the solar cell. For example, when a solution out of the above range is used, a rough surface can not be obtained, and a reduction in reflectivity can not also be obtained. When the acetic acid is less than about 1 wt%, a uniform etching surface can not be obtained due to a high etching rate, and when the acetic acid is more than about 10 wt%, the occurrence of surface defects is increased due to a low etching rate, The efficiency of the battery can be reduced.

According to one embodiment of the disclosure, the etch may be, but is not limited to, performed for about 2 minutes to about 60 minutes. For example, the etch may be performed for about 2 minutes to about 60 minutes, about 2 minutes to about 55 minutes, about 2 minutes to about 50 minutes, about 2 minutes to about 45 minutes, about 2 minutes to about 40 minutes, About 2 minutes to about 15 minutes, about 2 minutes to about 10 minutes, or about 2 minutes to about 30 minutes, about 2 minutes to about 30 minutes, about 2 minutes to about 25 minutes, about 2 minutes to about 20 minutes, But may be, but not limited to, about 5 minutes. For example, if the etch time is less than about 2 minutes, a spacing of about 100 nm and about 1 탆, which is the spacing of the pattern, may not be etched, and if the etch time is greater than about 60 minutes, It may proceed excessively, fail to maintain a constant aspect ratio, may have a low depth and a flat surface, and the generated microtasking may be etched to increase reflectivity.

In one embodiment of the present invention, micropatterning may be formed inside the pattern formed on the substrate, but the present invention is not limited thereto. For example, after the etching, not only a pattern is formed on the substrate surface, but also a fine-sized pyramid-shaped taxing pattern may be formed inside the pattern.

According to an embodiment of the present invention, the microtasking formed in the pattern may have a size of about 10 nm to about 1 탆, but may not be limited thereto. For example, the microtasking may be performed at a wavelength of from about 10 nm to about 1 m, from about 10 nm to about 900 nm, from about 10 nm to about 800 nm, from about 10 nm to about 700 nm, from about 10 nm to about 600 nm, From about 10 nm to about 500 nm, from about 10 nm to about 400 nm, from about 10 nm to about 300 nm, from about 10 nm to about 200 nm, from about 10 nm to about 100 nm, or from about 10 nm to about 50 nm But it may not be limited thereto.

Hereinafter, embodiments of the present invention will be described in detail. However, the present invention is not limited thereto.

[ Example ]

In this embodiment, a single crystal silicon wafer was used as a substrate. PR GXR 601 (Positive PR) manufactured by AZ ELECTRONIC MATERIALS Co., Ltd. was spin-coated at 500 rpm for 5 seconds on the surface of the substrate, followed by spin coating at 3,000 rpm for 30 seconds to apply PR to a thickness of 1.5 탆.

On the other hand, a mold was fabricated using polydimethylsiloxane (PDMS). The pattern of the mold was 1 μm in diameter, 10 μm in spacing, and 1 μm in height.

The mold having the hexagonal close-packed structure manufactured according to the present embodiment was contacted with the substrate coated with the PR, followed by the imprinting process.

The heat treatment proceeded while the mold and the substrate were in contact with each other. The heat treatment was carried out at 100 DEG C for 2 minutes, which is the temperature at which the PR can be cured. After the curing of the PR was completed, the mold was removed.

Subsequently, the substrate was immersed in an etching solution. The etching solution was HF: HNO₃: CH₃COOH = 100: 1.5: 5. The etching time was varied between 1 minute, 2 minutes, 4 minutes, 8 minutes and 10 minutes, After completion of the etching, the substrate was washed and the PR layer was removed.

In order to confirm the surface taxing effect according to the increase of the etching time, an SEM image was photographed as shown in FIGS. 3 to 6, and the reflectance measurement was performed as shown in FIGS.

FIG. 3A is a planar SEM image of the substrate surface after the surface taxing process according to the present embodiment, and FIG. 3B is a SEM image of the cross section. As shown in FIG. 3A, a hexagonal close-packed pattern was formed at regular intervals. As shown in FIG. 3B, microtasking was formed in the form of a pyramid of 10 nm to 10 μm at the same time as pattern formation of a hexagonal close- I could confirm. As shown in FIG. 3B, it can be seen that the size of the microtasking on the top is large and the size of the microtasking on the bottom is small. This is because the etching is performed at the base surface of the base material after taxing first, and thus the pyramid structure of the base material surface continues to be etched to increase the size.

Figs. 4A, 5A, and 6A are cross-sectional SEM images showing changes in surface pattern size when the etching time is changed to 2 minutes, 4 minutes, and 8 minutes, respectively, in this embodiment, and Figs. 4B, 6B are plane SEM images showing changes in the microtasking shape when the etching time is changed to 2 minutes, 4 minutes, and 8 minutes, respectively, in this embodiment. As shown in FIGS. 4A, 5A, and 6A, it was found that the size of the pattern was increased as the etching time was increased. When the etching was performed for 2 minutes as shown in FIG. 4B, the hemispherical pattern formation and the internal pyramid It was confirmed that the pattern size was increased and the size of micropatterning was increased when the etching was performed for 4 minutes as shown in FIG. 5B. As shown in FIG. 6B, Similarly, when the etching was performed for 8 minutes, the pattern size was increased, but the microtasking size was found to be similar. As a result, it was confirmed that the microtasking uniformity was increased.

7 and 8 are graphs showing changes in surface reflectance according to the etching time in this embodiment. As shown in FIGS. 7 and 8, it was confirmed that the surface reflectivity decreases as the etching time is increased by micro-tacking in the hole.

In the case of using alkaline SDR (wet etching), when the solar cell was fabricated using a single crystal wafer, the reflectivity was 10% or more. However, according to this example, the reflectivity of 10% or less was obtained.

It will be understood by those of ordinary skill in the art that the foregoing description of the embodiments is for illustrative purposes and that those skilled in the art can easily modify the invention without departing from the spirit or essential characteristics thereof. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is defined by the appended claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

10: substrate
20: Photoresist
30: Mold

Claims

Applying a photoresist to the substrate;
Forming a pattern on the substrate using a mold having a pattern of repeated structures, and then curing the pattern; And
The step of etching the substrate
Wherein the surface of the solar cell surface is touched.

The method according to claim 1,
Wherein the substrate comprises a material selected from the group consisting of monocrystalline, microcrystalline, polycrystalline, amorphous, and combinations thereof.

The method according to claim 1,
Wherein the pattern of the repeated structure comprises a hexagonal close-packed structure.

The method according to claim 1,
Wherein the pattern of the repeated structure has a size of 100 nm to 10 mu m.

The method according to claim 1,
Wherein the pattern of the repeated structure has an interval of 1 占 퐉 to 100 占 퐉.

The method according to claim 1,
Wherein a microtasking is formed inside the pattern formed on the substrate.

The method according to claim 6,
Wherein the microtasking formed in the pattern has a size of 10 nm to 1 占 퐉.

The method according to claim 1,
Wherein the forming of the pattern on the substrate is performed by a method selected from the group consisting of imprinting, lithography, gravure printing, roll-to-roll printing, and combinations thereof. .

The method according to claim 1,
Wherein the etching of the substrate is performed by a method selected from the group consisting of wet etching, dry etching, mechanical etching, and combinations thereof.

10. The method of claim 9,
Wherein the wet etching is performed using a mixed solution selected from the group consisting of hydrogen fluoride, nitric acid, acetic acid, and combinations thereof.

11. The method of claim 10,
Wherein the wet etching is performed using a solution containing 0.5 wt% to 5 wt% of the nitric acid with respect to 100 wt% of the hydrogen fluoride.

11. The method of claim 10,
Wherein the wet etching is performed using a solution containing 1 wt% to 10 wt% of the acetic acid with respect to 100 wt% of the hydrogen fluoride.

The method according to claim 1,
Wherein the etching is performed for 2 to 60 minutes.

The method according to claim 1,
Further comprising the step of removing the remaining film before the step of etching the substrate.