KR20110028101A - Textured glass for a thin film solar cell and preparation method of thin film solar cell using the same - Google Patents

Abstract

PURPOSE: A glass for a thin film solar cell substrate and a thin film solar cell with the same are provided to increase an effect for surrounding light, thereby increasing photoelectric transformation efficiency of a solar cell. CONSTITUTION: A texturing unit(200) comprises one or more uneven structures which are arranged on a substrate(100) at a fixed interval. A scribing unit(300) is formed between texturing units. The texturing unit comprises an uneven structure of pyramid, cone, or lenticular shapes. An interval between the scribing unit and the texturing unit is 5~100mm.

Description

Glass for a thin film solar cell substrate and a thin film solar cell including the same {Textured Glass for a Thin Film Solar Cell and Preparation Method of Thin Film Solar Cell using the same}

The present invention relates to a thin film solar cell glass and a thin film solar cell comprising the same, and more particularly, the scribing (scribing) to the textured glass, characterized in that there is no textured shape It relates to a thin film solar cell substrate glass and a thin film solar cell comprising the same.

Interest in renewable energy is increasing due to high oil prices and environmental problems. Unlike other energy sources, solar cells, which are photovoltaic devices that convert sunlight into electrical energy, are endless and environmentally friendly, and their importance is increasing over time.

Solar cells can be classified into crystalline solar cells using wafers used in semiconductors and thin film solar cells using deposition techniques on substrates such as glass. Although crystalline solar cells currently have a high market share, the market share of thin film solar cells is expected to increase in the future due to high efficiency and low price.

Texturing techniques in solar cells have been used in various ways to improve solar cell efficiency by increasing light scattering to increase light confinement effects. As a texturing method, US Pat. No. 9,918,030 discloses a technique for etching and texturing a wafer used in a solar cell with an acidic acid solution. When the transparent electrode is formed on the glass, it is deposited using atmospheric pressure plasma chemical vapor deposition (APCVD) or sputtered (Sputteirng) and then subjected to acidic etching to prepare a textured transparent electrode glass. US Pat. No. 7,368,655 discloses a pyramidal textured textured panel for use in crystalline solar cells.

As such, the technique of texturing the electrode may improve the photoelectric conversion efficiency by increasing light scattering in the crystalline solar cell, but in the case of the thin film solar cell, the scribing process of forming the electrode due to the texturing structure of the glass This is impossible, so it cannot be used in thin film solar cells. The texturing structure also scatters the light of the scribing laser and thus cannot insulate between the unit cells, and in the case of mechanical scribing, the texturing cannot properly scribe.

The present invention is to overcome the above-mentioned problems of the prior art, one object of the present invention is to provide a texturing effect and scribing of the glass at the same time by not texturing the scribing portion when manufacturing the textured glass It is to provide a glass for a thin film solar cell substrate that can provide a high efficiency thin film solar cell.

Another object of the present invention is to provide a thin film solar cell having an improved photoelectric conversion efficiency by including a scribing portion between the texturing portion.

Still another object of the present invention is to provide a method of manufacturing a solar cell which can improve the confinement effect of incident light and improve the photoelectric conversion efficiency of the solar cell.

One aspect of the present invention provides a thin film solar cell substrate glass comprising a texturing portion including at least one uneven structure and an untextured scribing portion formed between the texturing portions, arranged at regular intervals. It is about.

Another aspect of the invention is a substrate; A transparent electrode formed on the substrate; A light absorption layer formed on the transparent electrode; And a back electrode formed on the light absorption layer, the substrate relates to a thin film solar cell comprising the glass.

Yet another aspect of the present invention provides a method for preparing a substrate comprising: preparing a substrate including a texturing portion including at least one uneven structure and an untextured scribing portion formed between the texturing portions;

Scribing after forming a transparent electrode layer on the substrate;

Scribing after forming a light absorption layer on the transparent electrode layer;

Scribing after forming a back electrode on the photo-moisture layer; And

 It relates to a method for manufacturing a thin film solar cell comprising the step of etching the edge portion of the obtained solar cell by edge isolation.

The glass for thin film solar cell substrate of the present invention includes a scribing portion of a flat structure that is not textured between the texturing portions, and a thin film solar cell having high photoelectric conversion efficiency when the transparent electrode is deposited on the glass of the present invention and used in the thin film solar cell. Can be provided. In addition, it is possible to replace the existing expensive transparent electrode can reduce the manufacturing cost when manufacturing a thin film solar cell.

Hereinafter, a glass, a thin film solar cell and a method for manufacturing the thin film solar cell substrate according to the present invention will be described in detail with reference to the accompanying drawings.

In order to clearly describe the present invention, parts irrelevant to the description are omitted, and in order to clearly express various layers and regions in the drawings, thicknesses are enlarged.

In addition, all terms including technical terms and scientific terms used below have the same meaning as commonly understood by one of ordinary skill in the art.

In one aspect, the glass for a thin film solar cell substrate of the present invention includes a concave-convex structure capable of scattering light by texturing other portions except a scribed section. Conventional texturing glass cannot be used for thin film solar cells because scribing is impossible, but the glass for thin film solar cell substrate of the present invention can give a texturing effect and scribing at the same time, and thus is highly applicable to thin film solar cells. Photoelectric conversion efficiency can be achieved.

1A-1B are schematic perspective views of a glass for a thin film solar cell substrate according to an embodiment of the present invention. FIG. 1A is a schematic perspective view of a substrate on which a texturing portion is embossed, and FIG. 1B is a schematic perspective view of a substrate on which a texturing portion is intaglio.

Referring to FIG. 1, a glass for a thin film solar cell substrate according to an embodiment of the present invention includes a texturing unit 200 including at least one uneven structure and disposed between the texturing units and one or more uneven structures disposed on the substrate 100 at regular intervals. Formed untextured scribing unit 300.

Thin film solar cells are manufactured by forming a thin film on a substrate, which is generally a glass substrate. The thin film of the thin-film solar cell basically consists of a silicon thin film that absorbs light to generate electrons and holes, and above and below the electrode to transfer the electrons and holes produced here. Since the upper electrode must pass light to the silicon film, a transparent conductive oxide film (TCO-Transparent Conductive Oxide) is used. Since there is not enough voltage and output when only a thin film is coated, it is divided into small long strip-shaped cells and connected in series. Laser scribing technology is used to divide the thin film into unit cells. Since the glass for the thin film solar cell substrate of the present invention includes an untextured flat portion for the scribing process between the texturing parts 200, the high efficiency of the thin film solar cell can be achieved by simultaneously enabling the texturing effect and the scribing. It can be realized.

The method of manufacturing the glass for the thin film transistor of the present invention is not particularly limited, but, for example, a scribing part having a predetermined width between the texturing parts 200 by an imprinting method, a hot press method, a photolithography method, and a silk screen method. 300 may be formed to lie.

2A-2B are schematic perspective views of texturing portions of a substrate of one embodiment of the present invention, and FIGS. 2C-2D are schematic perspective views of texturing portions of a substrate of another embodiment of the present invention.

The shape of the texturizing unit 200 may be formed in various shapes such as pyramid shape, cone shape, lens shape, etc. as shown in FIGS. 2A and 2B, and the incident shape such as the square pyramid shape in which the portion is cut as shown in FIG. 2C or 2D. It can be implemented in any form that can scatter the sunlight.

In the present invention, the texturing unit 200 may be configured by using embossed, intaglio or embossed and intaglio. For example, as shown in FIG. 1A, it may be configured as an embossment 200, as shown in FIG. 1B, and may be formed as an intaglio 200 ′, and a combination of an embossment and an intaglio may be used.

Assuming that the shape of the texturing unit 200 is a pyramid shape, in the case of a pyramid shape, the scattering effect of light is reduced when the texturing angle is too wide, such as 80 degrees or more, preferably between 10 degrees and 75 degrees. Do.

The distance between the texturing part 200 and the scribing part 300 may be about 5 to 100 mm, preferably about 3 mm to 20 mm, and more preferably about 5 mm to 15 mm. The scribing unit 300 is called a dead zone that does not generate power, and the narrower the narrower the insulation area is, the better. The width of the scribing unit 300 may be from 70 μm to 1,000 μm, preferably about 100 to 500 μm. The number of texturing of the texturing part 200 varies depending on the patterning shape, but is applicable to 2 to 20,000 pieces per mm, preferably 100 to 10,000 pieces.

Another aspect of the invention relates to a thin film solar cell comprising the glass for the substrate. 3 is a schematic cross-sectional view of a thin film solar cell of one embodiment of the present invention. Referring to FIG. 3, the solar cell of the present invention includes a substrate 10; A transparent electrode 20 formed on the substrate; A light absorption layer 30 formed on the transparent electrode; And a back electrode 40 formed on the light absorption layer, wherein the substrate is disposed at regular intervals, the texturing portion 11 including at least one uneven structure and an untextured flat surface formed between the texturing portions. It includes a crushing unit (13).

The texturing part 11 of the substrate is mainly formed to prevent reflection of the light-receiving surface of the solar cell, and the shape of the texturing part is not particularly limited, and may be any shape such as trapezoid, pyramid, conical flat, and the like.

The transparent electrode 20 is composed of a transparent electrode for passing light incident from the outside to the light absorbing layer 30, and a conductive material coated on the substrate to pass light includes indium tin oxide (ITO), Florin doped tin oxide (FTO), ZnO, ZnO: B, ZnO: Al, SnO ₂ , ZnO-Ga, ZnO-Ga ₂ O ₃ , ZnO-Al ₂ O ₃ , SnO ₂ : F, SnO ₂ -Sb ₂ O ₃ may be used, but is not necessarily limited thereto. Such a transparent electrode may be formed by a sputtering process or a vacuum deposition method.

The light absorption layer 30 is formed on the transparent electrode 20, and is a PIN bonding layer bonded with N-type, I-type, and P-type silicon layers by a CVD process such as a plasma CVD process or an inductively coupled plasma CVD process. Can be formed. Specifically, the light absorption layer 30 forms an N-type silicon layer on the transparent electrode 20, and then forms an I-type silicon layer on the N-type silicon layer, and then forms a P-type on the I-type silicon layer. It can be configured by forming a silicon layer. The N-type silicon layer is a layer doped with N-type impurities such as phosphorus and nitrogen, and the P-type silicon layer is a layer doped with a P-type impurity, which is a Group 3 element such as boron. In addition, the light absorption layer 30 may be formed of a CuInGaSe or CdTe compound semiconductor layer.

The semiconductor layer generates holes and electrons by sunlight, and the generated holes and electrons are collected in the P layer and the N layer, respectively. In order to enhance the efficiency of collecting holes and electrons, The PIN structure is more preferable than the PN structure consisting of only N layers. When the first semiconductor layer is formed in a PIN structure, the I layer is depleted by the P layer and the N layer to generate an electric field therein, and the holes and electrons generated by sunlight are generated by the electric field. Drift by to collect in the P and N layers, respectively.

The back electrode 40 of the conductive material is formed on the light absorption layer 30. This back electrode is formed using a transparent electrode to pass the light incident from the outside to the light absorption layer 30, it is preferable to form the back electrode 40 using the ITO electrode to pass the light, its Formation may use a sputtering process or a vacuum deposition method.

In the solar cell of the present invention, the back electrode 40 is formed using a metal such as Ag or Al, and the sunlight passing through the front electrode 20 and the light absorption layer 30 is reflected by the back electrode 40. And re-incident to the light absorption layer 30.

The solar cell configured as described above operates as follows. When light is incident on the solar cell from the outside, electrons and holes are generated by the light energy incident from the light absorption layer 30, and the electrons are diffused into the N-type silicon layer and the holes are respectively diffused into the P-type silicon layer. When polarization of the charge carriers occurs, a potential difference occurs on both sides of the semiconductor. At this time, when the N-type silicon layer and the P-type silicon layer are connected, electric power is generated by the movement of the electrons and holes.

Another aspect of the invention relates to a method of manufacturing a solar cell. 4 is a manufacturing process flowchart of the manufacturing method of the thin film solar cell of the present invention.

When manufacturing a solar cell by the method of the present invention, a thin film solar cell substrate comprising a texturing portion including at least one uneven structure, and an untextured scribing portion formed between the texturing portions, which are first disposed at regular intervals. Prepare a glass for (S1). Subsequently, the transparent electrode is formed on the glass and then scribed (S2). Subsequently, an N-type silicon layer, an I-type silicon layer, and a P-type silicon layer are sequentially formed on the transparent electrode to form a light absorption layer, and then scribe. Subsequently, a rear electrode is formed on the light absorption layer (S4).

In the present invention, an anti-reflection film may be formed on the rear electrode. The anti-radiation film may include, for example, a material selected from the group consisting of silicon nitride film, silicon nitride film including hydrogen, silicon oxide film, silicon oxynitride film, MgF ₂ , ZnS, MgF ₂ , TiO ₂ and CeO ₂ . The anti-reflection film may be formed by vacuum deposition, chemical vapor deposition, spin coating, screen printing or spray coating, but is not necessarily limited thereto.

In the case of manufacturing a solar cell according to the present invention, a substrate is first prepared. First, various impurities remaining on the surface of the glass substrate are removed in order to increase the bonding force with the thin film to be formed later as a pretreatment. In this case, for example, impurities existing on the glass substrate may be removed by a wet cleaning method, and dried in a predetermined gas atmosphere.

The transparent electrode includes indium tin oxide (ITO), florine doped tin oxide (FTO), ZnO, ZnO: B, ZnO: Al, SnO ₂ , ZnO-Ga, ZnO-Ga ₂ O ₃ , ZnO-Al ₂ O ₃ , A transparent conductive material such as SnO ₂ -Sb ₂ O ₃ may be formed using a sputtering method or a metal organic chemical vapor deposition (MOCVD) method, and the thickness thereof is preferably in the range of 500 to 10000 Pa.

The light absorption layer 30 may be formed of a semiconductor material, such as silicon-based, CuInSe ₂ -based, CdTe-based by using a plasma CVD method, and has a PIN structure in which the semiconductor material is laminated with a P layer, an I layer, and an N layer. It is preferable to form. When the light absorption layer 30 has a PIN structure, it is preferable to form a P layer on the transparent electrode layer 20, an I layer on the P layer, and an N layer on the I layer. The reason is that the drift mobility of the holes is generally low due to the drift mobility of the electrons, so that the P layer is formed close to the light receiving surface in order to maximize the collection efficiency by incident light.

The back electrode 40 may be formed of a metal such as Ag, Al, Ag + Mo, Ag + Ni, Ag + Cu, etc. using a sputtering method or a printing method. Like the transparent electrode 20 described above, the rear electrode 40 is formed by sputtering or MOCVD of a transparent conductive material such as ZnO, ZnO: B, ZnO: Al, SnO ₂ , SnO ₂ : F, or Indium Tin Oxide (ITO). The conductive film may be formed using a (Metal Organic Chemical Vapor Deposition) method or the like.

Then, when the thin film solar cell module is completed, the edge is next isolated. The edge isolation process is to prevent the front electrode and the rear electrode may be electrically connected when the same conductivity type is formed on the entire surface of the semiconductor substrate. The edge isolation process can be performed using a vacuum plasma or laser.

Hereinafter, the embodiments of the present invention will be described in more detail, but these embodiments are only for illustrating the present invention and the present invention is not limited thereto.

Example  One

Flat glass with a thickness of 4 mm is placed in a furnace and heated to a glass transition temperature. When the glass transition is heated to a temperature, the template on which the texturing section 10 mm and the scribing section 500 μm without the texturing section is formed is pressed on the heated glass to form a pattern on the glass. The number of texturing intervals is 100. After the glass was cut to 200 × 200 mm, aluminum doped zinc oxide (ZnO: Al) was deposited by about 1 mm with a transparent electrode, and a PIN, which is a light absorption layer, was deposited by chemical vapor deposition.

On the glass on which the transparent electrode was deposited, a SiC layer was deposited to a thickness of 90 to 150 kHz by RF PECVD using monosilane, hydrogen, diborane, and methane gas. Type I silicon layer formed the intrinsic layer of 2500-3000 GPa thickness using monosilane and hydrogen. The N-type silicon layer was formed using a monosilane, hydrogen, phosphine gas to form an N-type silicon layer of 300 ~ 350 ~ thickness. The RF PECVD apparatus used was composed of multi chambers to prevent contamination due to interlayer doping.

After deposition of the light absorbing layer, silver (Ag) was deposited on the rear electrode by sputtering to manufacture a solar cell module. In order to insulate the transparent electrode, the light absorbing layer, and the back electrode after deposition, scribing was performed using a laser having 1032 nm for the transparent electrode and 532 nm for the light absorbing layer and the back electrode in each step. edge isolation was performed. The measured module measured the photoelectric conversion efficiency and the output (W) using a solar simulator and the results are shown in Table 1 below.

Photoelectric conversion efficiency was measured under standard test conditions. Standard test conditions were air mass 1.5, irradiation intensity 100mW / ㎠, temperature 25 degrees, and the current and voltage were measured after light irradiation. Light irradiation was measured using a Wacom (WXS-200S) device capable of measuring a size of 200x200mm. The measurement was performed by using a metal ribbon on the front and rear electrodes of the module to draw the electrodes to the outside, and placed them at the bottom of the solar simulator. . The output characteristics of the solar cell are calculated by the following equation on the basis of the output current and the output voltage on the output current voltage curve obtained using the solar simulator.

In the above formula, I _p : Output current, V _p : output voltage, S: device area,

I: irradiation intensity of light irradiated by solar cells

Example  2

In Example 1, the width of the texturing part and the scribing part were the same, and the number of texturings was set to 1000, and the thin film solar cell module was manufactured in the same manner except that the pyramid structure was textured by 10 μm. Photoelectric conversion efficiency and output (W) were measured and the results are shown in Table 1 together.

  .

Example  3

In Example 1, the width of the texturing part and the scribing part were the same, and the number of texturings was 10,000, so that the thin film solar cell module was manufactured in the same manner except that the pyramid structure was textured by 1 μm. Photoelectric conversion efficiency and output (W) were measured and the results are shown in Table 1 together.

Comparative example  One

The thin film solar cell module was fabricated in the same manner except for using the textured glass without the scribing section, and the photoelectric conversion efficiency and output (W) were measured and the results are shown in Table 1 together.

Comparative example  2

In Example 1, the widths of the texturing part and the scribing part are the same, and the number of texturing parts is equal to 2, and the thin film solar cell module is manufactured by performing the same procedure except that the pyramid structure uses 5 mm textured glass. The conversion efficiency and output (W) were measured and the results are shown in Table 1 together.

Comparative example  3

A thin film solar cell module was fabricated in the same manner except that a commercially available transparent electrode (VU type, manufactured by Asahi) was used by depositing a transparent conductive oxide material on flat glass and etching the same. And, the photoelectric conversion efficiency and output (W) were measured and the results are shown in Table 1 together.

As shown in Table 1, in the case of the textured glass not made along the scribing section as in Comparative Example 1, the short between the cells occurred, the efficiency was not measured, and in the case of Comparative Example 2 having a large pyramid structure There was no improvement compared to Comparative Example 3 using the conventional commercially available transparent electrode glass. However, Example 1, Example 2, and Example 3 using the glass of the present invention achieved high photoelectric conversion efficiency as compared with Comparative Example 3.

What has been described above is merely an example for explaining the solar cell according to the present invention, and the present invention is not limited to the above-described embodiment, and as claimed in the following claims without departing from the gist of the present invention. It is natural that anyone skilled in the art belongs to the scope of the present invention to the extent that various modifications can be made.

1A-1B are schematic perspective views of a glass for a thin film solar cell substrate according to an embodiment of the present invention. FIG. 1A is a schematic perspective view of a substrate on which a texturing portion is embossed, and FIG. 1B is a schematic perspective view of a substrate on which a texturing portion is intaglio.

2A-2B are schematic perspective views of texturing portions of a substrate of one embodiment of the present invention, and FIGS. 2C-2D are schematic perspective views of texturing portions of a substrate of another embodiment of the present invention.

3 is a schematic cross-sectional view of a thin film solar cell of one embodiment of the present invention.

4 is a manufacturing process flowchart of the manufacturing method of the thin film solar cell of the present invention.

* Description of the symbols for the main parts of the drawings *

100: substrate 200: texturing portion 300: scribing portion

10: substrate 20: transparent electrode layer 11: texturing portion

13: scribing unit 30: light absorption layer 40: rear electrode

Claims (10)

A glass for a thin film solar cell substrate comprising a texturing portion including at least one uneven structure and an untextured scribing portion formed between the texturing portions disposed at regular intervals. The glass of claim 1, wherein the texturing part comprises a pyramidal, conical, or lenticular structure. The glass of claim 1, wherein the concave-convex structure of the texturing portion is embossed, engraved or engraved. The glass of claim 1, wherein a distance between the texturing part and the scribing part is 5 to 100 mm. The glass of claim 1, wherein the width of the scribing portion is 100 μm to 500 μm. Board; A transparent electrode formed on the substrate; A light absorption layer formed on the transparent electrode; And a back electrode formed on the light absorption layer, wherein the substrate is made of any one of claims 1 to 4, wherein the thin film solar cell. Preparing a substrate including a texturing portion including at least one uneven structure and an untextured scribing portion formed between the texturing portions and disposed at regular intervals; Scribing after forming a transparent electrode layer on the substrate; Scribing after forming a light absorption layer on the transparent electrode layer; Scribing after forming a back electrode on the photo-moisture layer; And  Method of manufacturing a thin film solar cell comprising the step of etching the edge portion of the obtained solar cell by edge isolation. The method of claim 1, wherein the forming of the substrate is performed by an imprint method, a hot press method, a photolithography method, or a silk print method. The solar cell of claim 1, wherein the forming of the scribing part is etched by plasma etching or chemical etching. The method of claim 6, wherein the method further comprises forming an anti-reflection film on the back electrode.

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