KR101032433B1 - Thin film type Solar Cell and Method for manufacturing the same - Google Patents

Abstract

The present invention is a substrate; A light scattering film formed on the substrate and including a bead and a binder to fix the bead; A front electrode layer formed on the light scattering film, the surface of which has a concave-convex structure; A semiconductor layer formed on the front electrode layer; And a back electrode layer formed on the semiconductor layer, wherein the uneven structure is formed on one surface of the front electrode layer in contact with the semiconductor layer and is not formed on the other surface of the front electrode layer in contact with the light scattering film. As a thin film solar cell, and a manufacturing method thereof,
According to the present invention, by forming a light scattering film between the substrate and the front electrode layer can be variously refracted sunlight can lengthen the path of sunlight incident to the semiconductor layer, and also, the light scattering film barrier (barrier) during the front electrode layer deposition process It acts as) to block the movement of impurities contained in the substrate to the front electrode layer has the effect of improving the efficiency of the solar cell.

Description

Thin film type solar cell and method for manufacturing same

The present invention relates to a solar cell, and more particularly to a thin film solar cell.

Solar cells are devices that convert light energy into electrical energy using the properties of semiconductors.

The structure and principle of the solar cell will be briefly described. The solar cell has a PN junction structure in which a P (positive) type semiconductor and a N (negative) type semiconductor are bonded to each other. Holes and electrons are generated in the semiconductor by the energy of the incident solar light. At this time, the holes (+) are moved toward the P-type semiconductor by the electric field generated in the PN junction. Negative (-) is the principle that the electric potential is generated by moving toward the N-type semiconductor to generate power.

Such a solar cell can be classified into a substrate type solar cell and a thin film solar cell.

The substrate type solar cell is a solar cell manufactured by using a semiconductor material such as silicon as a substrate, and the thin film type solar cell is a solar cell manufactured by forming a semiconductor in the form of a thin film on a substrate such as glass.

Substrate-type solar cells, although somewhat superior in efficiency compared to thin-film solar cells, there is a limitation in minimizing the thickness in the process and there is a disadvantage that the manufacturing cost is increased because of the use of expensive semiconductor substrates.

Although thin-film solar cells are somewhat less efficient than substrate-type solar cells, they can be manufactured in a thin thickness and inexpensive materials can be used to reduce manufacturing costs, making them suitable for mass production.

Hereinafter, a thin film solar cell according to the related art will be described with reference to the accompanying drawings.

1 is a schematic cross-sectional view of a thin film solar cell according to a conventional embodiment.

As can be seen in FIG. 1, in the thin film solar cell according to the related art, the front electrode layer 30 is formed on the substrate 10, and the semiconductor layer 40 is formed on the front electrode layer 30. The transparent conductive layer 50 is formed on the semiconductor layer 40, and the rear electrode layer 60 is formed on the transparent conductive layer 50.

However, such a conventional thin film solar cell has the following problems.

First, in order to improve the efficiency of the solar cell, it is necessary to increase the generation rate of holes and electrons in the semiconductor layer 40 by lengthening the path through which the sunlight passes through the semiconductor layer 40. . However, the conventional thin-film solar cell has a problem in that it is not possible to form a long path of sunlight in the semiconductor layer 40 and thus does not obtain battery efficiency as desired.

Second, in general, the substrate 10 uses glass, and alkali ions are contained in the glass, and the alkali ions move to the front electrode layer 30 in the process of high temperature deposition and impurity. As a result, there is a problem that the efficiency of the solar cell is lowered.

The present invention has been devised to solve the conventional problems as described above, the present invention is to provide a thin-film solar cell and a method of manufacturing the same that can increase the efficiency of the solar cell by increasing the path of sunlight in the semiconductor layer. The purpose.

Another object of the present invention is to provide a thin film solar cell and a method of manufacturing the same, which can increase the efficiency of a solar cell by preventing the alkali ions contained in the substrate from moving to the front electrode layer.

The present invention, in order to achieve the above object; A light scattering film formed on the substrate and including a bead and a binder to fix the bead; A front electrode layer formed on the light scattering film, the surface of which has a concave-convex structure; A semiconductor layer formed on the front electrode layer; And a back electrode layer formed on the semiconductor layer, wherein the uneven structure is formed on one surface of the front electrode layer in contact with the semiconductor layer and is not formed on the other surface of the front electrode layer in contact with the light scattering film. Provides a thin film solar cell.

The invention also provides a substrate; A light scattering film formed on the substrate and including a bead and a binder to fix the bead; A front electrode layer formed on the light scattering film, the surface of which has a concave-convex structure; A first semiconductor layer formed on the front electrode layer; A buffer layer formed on the first semiconductor layer; A second semiconductor layer formed on the buffer layer; And a back electrode layer formed on the second semiconductor layer.

The invention also provides a substrate; A light scattering film formed on the substrate and including a bead and a binder to fix the bead; A front electrode layer formed on the light scattering film, the surface of which has a concave-convex structure; A semiconductor layer formed on the front electrode layer; And a back electrode layer formed on the semiconductor layer, wherein the beads contact the substrate and the front electrode layer, and the beads contacting the substrate and the front electrode layer have different refractive indices from the substrate and the front electrode layer. It provides a thin film solar cell.

The present invention also provides a process for forming a light scattering film comprising a bead and a binder for fixing the bead on a substrate; Forming a front electrode layer having a concave-convex structure on a surface of the light scattering film; Forming a semiconductor layer on the front electrode layer; And forming a back electrode layer on the semiconductor layer, wherein the uneven structure is formed on one surface of the front electrode layer in contact with the semiconductor layer and is not formed on the other surface of the front electrode layer in contact with the light scattering film. Provided is a method of manufacturing a thin film solar cell.

The present invention also provides a process for forming a light scattering film comprising a bead and a binder for fixing the bead on a substrate; Forming a front electrode layer having a concave-convex structure on a surface of the light scattering film; Forming a first semiconductor layer on the front electrode layer; Forming a buffer layer on the first semiconductor layer; Forming a second semiconductor layer on the buffer layer; And it provides a method for manufacturing a thin film solar cell comprising the step of forming a back electrode layer on the second semiconductor layer.

The present invention also provides a process for forming a light scattering film comprising a bead and a binder for fixing the bead on a substrate; Forming a front electrode layer having a concave-convex structure on a surface of the light scattering film; Forming a semiconductor layer on the front electrode layer; And forming a back electrode layer on the semiconductor layer, wherein the beads contact the substrate and the front electrode layer, and the beads contacting the substrate and the front electrode layer have different refractive indices from the substrate and the front electrode layer. It provides a method for manufacturing a thin film solar cell, characterized in that.

According to the present invention as described above has the following effects.

According to the present invention, by forming a light scattering film between the substrate and the front electrode layer, the sunlight can be variously refracted to lengthen the path of sunlight in the semiconductor layer. Therefore, the efficiency of the solar cell is improved.

In addition, by appropriately changing the material and pattern of the beads and the binder constituting the light scattering film can be easily adjusted the refractive pattern of the solar light it is possible to optimize the efficiency of the solar cell.

In addition, in the present invention, since the light scattering film is formed between the substrate and the front electrode layer, the light scattering film acts as a barrier in the process of depositing the front electrode layer so that impurities contained in the substrate move to the front electrode layer. It is blocked, there is an effect that the degradation of the efficiency of the solar cell is prevented.

1 is a schematic cross-sectional view of a thin film solar cell according to a conventional embodiment.
2 is a schematic cross-sectional view of a thin film solar cell according to an embodiment of the present invention.
3A-3C are cross-sectional views of beads according to various embodiments of the present invention.
4A to 4E are cross-sectional views illustrating a manufacturing process of a thin film solar cell according to an embodiment of the present invention.

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

<Thin Film Solar Cell>

2 is a schematic cross-sectional view of a thin film solar cell according to an embodiment of the present invention.

As can be seen in Figure 2, the thin-film solar cell according to an embodiment of the present invention, the substrate 100, the light scattering film 200, the front electrode layer 300, the semiconductor layer 400, the transparent conductive layer 500, and the back It comprises an electrode layer 600.

The substrate 100 mainly uses glass, but may also use transparent plastic.

The light scattering layer 200 is formed on the substrate 100 and includes a bead 220 and a binder 240. The light scattering layer 200 scatters the sunlight passing through the substrate 100 at various angles and prevents impurities contained in the substrate 100 from moving to the front electrode layer 300. do.

First, the light scattering film 200 will be described for scattering the sunlight passing through the substrate 100 at various angles as follows.

The light scattering layer 200 includes a bead 220 and a binder 240. The binder 240 is mainly in contact with the substrate 100 and the front electrode layer 300. In this case, when a material having a refractive index different from that of the substrate 100 and the front electrode layer 300 is used as a material constituting the binder 240, sunlight transmitted through the substrate 100 may be formed. Since the light is refracted while passing through the binder 240 and the light transmitted through the binder 240 is refracted again while passing through the front electrode layer 300, the light incident on the substrate 100 is eventually reduced. As the light is refracted at various angles, the light is incident on the semiconductor layer 400 so that the path of sunlight in the semiconductor layer 400 is long.

In some cases, the bead 220 may come into contact with the substrate 100 and the front electrode layer 300. In this case, the substrate 100 and the substrate may be formed of a material constituting the bead 220. When the material constituting the front electrode layer 300 and a material having a different refractive index are used, the solar light incident on the substrate 100 is refracted at various angles by the same mechanism as described above and is incident on the semiconductor layer 400. The path of sunlight in the semiconductor layer 400 is long.

In general, since the refractive index of the glass constituting the substrate 100 is about 1.52, and the refractive index of the front electrode layer 300 is about 1.9 to 2.0, the range of the refractive index of the substrate 100 and the front electrode layer 300 is In consideration of this, the material of the bead 220 or the binder 240 may be selected. Examples of the bead 220 may include SiO ₂ , TiO ₂ , CeO ₂ , and the like, and examples of the binder 240 may include silicates, but are not necessarily limited thereto.

In addition, when the beads 220 and the binder 240 constituting the light scattering film 200 are made of materials having different refractive indices from each other, sunlight may be variously refracted in the light scattering film 200. That is, when the beads 220 are made of a material having a different refractive index than that of the binder 240, the sunlight transmitted through the beads 220 is refracted while passing through the binder 240, and the binder ( Since the sunlight transmitted through the 240 is refracted while passing through the bead 220, the sunlight may be variously refracted.

In addition, instead of forming the beads 220 with the same material, when a plurality of beads having different refractive indices are used in combination with each other, sunlight may be refracted at various angles while passing through the beads 220 having different values from each other. .

In addition, the bead 220 may be composed of a core part and a skin part, so that sunlight may be refracted at various angles while passing through one bead 220. That is, FIGS. 3A to 3C are cross-sectional views of the beads 220 according to various embodiments of the present disclosure. As shown in FIG. 3A, the beads 220 may include a core part 222 and the core part ( It is composed of a skin portion 224 surrounding the 222, the material of the core portion 222 by using a material that is different in refractive index from the material of the skin portion 224, the sunlight to the skin portion 224 After passing through the core portion 222 may be refracted, and after passing through the core portion 222 may be refracted again when passing through the skin portion 224. In addition, as can be seen in Figure 3b, the core portion 222 is made of air so that the same effect can be obtained by using the hollow bead 220 consisting of only the skin portion 224. In some cases, as shown in FIG. 3C, the core part 222 may be formed of a plurality of material layers 222a and 222b having different refractive indices, and the skin part 224 may have a plurality of different refractive indices. It may be composed of material layers 224a and 224b. In addition, by changing the cross-section of the bead 220 in a variety of forms, such as circular, elliptical may be variously changed the angle of refraction of sunlight.

In addition, as shown in the enlarged view of FIG. 2, the light scattering film 200 may be formed to have a concave-convex structure so that the refractive angle of solar light may be variously changed.

Next, when the light scattering film 200 prevents the impurities contained in the substrate 100 from moving to the front electrode layer 300, the light scattering film 200 is the substrate 100 and the Since it is formed between the front electrode layer 300, during the deposition process of the front electrode layer 300, the light scattering film 200, in particular the binder 240 constituting the light scattering film 200 acts as a barrier (barrier) Impurities contained in the substrate 100 are blocked from moving to the front electrode layer 300.

The front electrode layer 300 is formed on the light scattering film 200, and is formed on the surface where the sunlight is incident, ZnO, ZnO: B, ZnO: Al, SnO ₂ , SnO ₂ : F or ITO (Indium Tin Oxide) It may be formed using a transparent conductive material such as.

The surface of the front electrode layer 300 is formed with a concave-convex structure, and the scattering of the incident sunlight due to the concave-convex structure in various ways to increase the absorption rate of the sunlight in the semiconductor layer 400.

Meanwhile, when the uneven structure of the front electrode layer 300 is formed too large, defects may occur in the semiconductor layer 400 and the transparent conductive layer 500 formed on the front electrode layer 300. Efficiency may be reduced. In the present invention, since the scattering effect of sunlight can be sufficiently obtained by the light scattering film 200, it is not necessary to form an uneven structure largely on the surface of the front electrode layer 300, thus the front electrode layer 300 The uneven structure of the surface is preferably adjusted so small that defects do not occur in the semiconductor layer 400 and the transparent conductive layer 500.

The semiconductor layer 400 is formed on the front electrode layer 300, and as the surface of the front electrode layer 300 is formed in an uneven structure, the surface of the semiconductor layer 400 is also formed in an uneven structure.

The semiconductor layer 400 has a PIN structure in which a P (positive) type semiconductor layer, an I (intrinsic) type semiconductor layer, and an N (negative) type semiconductor layer are sequentially stacked. As described above, when the semiconductor layer 400 has a PIN structure, the I-type semiconductor layer is depleted by the P-type semiconductor layer and the N-type semiconductor layer to generate an electric field therein, and is generated by sunlight. As the holes and electrons are drift by the electric field, holes are collected to the front electrode layer 300 through the P-type semiconductor layer and electrons are collected to the back electrode layer 600 through the N-type semiconductor layer. On the other hand, when the semiconductor layer 400 is formed in a PIN structure, it is preferable to form a P-type semiconductor layer on the front electrode 300 and then to form an I-type semiconductor layer and an N-type semiconductor layer. In general, since the drift mobility of the holes is low due to the drift mobility of the electrons, the P-type semiconductor layer is formed close to the light receiving surface in order to maximize the collection efficiency due to incident light.

The transparent conductive layer 500 is formed on the semiconductor layer 400 and may be made of a transparent conductive material such as ZnO, ZnO: B, ZnO: Al, SnO ₂ , SnO ₂ : F, or Indium Tin Oxide (ITO). . The surface of the transparent conductive layer 500 is also formed of an uneven structure, the transparent conductive layer 500 can be omitted.

The back electrode layer 600 is formed on the transparent conductive layer 500 and may be made of a metal such as Ag, Al, Ag + Mo, Ag + Ni, Ag + Cu.

<Method of manufacturing thin film solar cell>

4A to 4E are cross-sectional views illustrating a manufacturing process of a thin film solar cell according to an embodiment of the present invention.

First, as shown in FIG. 4A, a light scattering layer 200 including a bead 220 and a binder 240 fixing the beads 220 is formed on the substrate 100.

The light scattering layer 200 may be uniformly distributed on the binder 240 to prepare a paste, and then may be formed using a printing method using such a paste, or a sol-gel (Sol- It may be formed using a gel method, a dip coating method, or a spin coating method. In forming the light scattering film 200, after forming the film in the same manner as described above, the bonding force between the substrate 100 and the light scattering film 200 by additionally performing an infrared firing process or a low temperature / high temperature firing process It is desirable to promote

The light scattering film 200 can be formed in the concave-convex structure as can be seen in the enlarged view, in this case, the printing method, the sol-gel method, dip coating After performing the method or the spin coating method (Spin Coating), the surface of the film may be formed into a concave-convex structure by physical contact.

Since the bead 220 and the binder 240 constituting the light scattering film 200 are the same as described above, a detailed description thereof will be omitted.

Next, as can be seen in Figure 4b, the front electrode layer 300 is formed on the light scattering film 200.

The front electrode layer 300 is laminated using a transparent conductive material such as ZnO, ZnO: B, ZnO: Al, SnO ₂ , SnO ₂ : F or ITO (Indium Tin Oxide), and the surface thereof is formed with an uneven structure. .

As such a method of forming the front electrode layer 300 having a concave-convex structure, the front electrode layer having the concave-convex structure may be directly controlled by appropriately adjusting the deposition conditions during a deposition process such as a metal organic chemical vapor deposition (MOCVD) process. There is a method of forming or forming a front electrode layer of a uniform surface through a deposition process such as a sputtering process and then forming the surface into an uneven structure through an etching process. The etching process may include an etching process using photolithography, anisotropic etching using a chemical solution, or an etching process using mechanical scribing.

As described above, the uneven structure of the surface of the front electrode 300 is preferably adjusted so small that defects do not occur in the semiconductor layer and the transparent conductive layer to be formed in a later process.

Next, as shown in FIG. 4C, the semiconductor layer 400 is formed on the front electrode layer 300.

The semiconductor layer 400 may be formed in a PIN structure in which a silicon-based amorphous semiconductor material is sequentially stacked with a P-type semiconductor layer, an I-type semiconductor layer, and an N-type semiconductor layer by using a plasma CVD method or the like.

Next, as can be seen in Figure 4d, to form a transparent conductive layer 500 on the semiconductor layer (400).

The transparent conductive layer 500 ZnO, ZnO: B, ZnO: Al, SnO 2, SnO 2: F , or ITO (Indium Tin Oxide) Metal (a transparent conductive material sputtered (Sputtering) method, such as or MOCVD Organic Chemical Vapor Deposition It can be formed by laminating using a) method or the like. The transparent conductive layer 500 forming process can be omitted.

Next, as can be seen in Figure 4e, to form a back electrode layer 600 on the transparent conductive layer (500).

The back electrode layer 600 may be formed by stacking a metal such as Ag, Al, Ag + Mo, Ag + Ni, Ag + Cu using a sputtering method or a printing method.

The foregoing has described the thin film solar cell and its manufacturing method according to an embodiment of the present invention, but the present invention is not limited to the above-described embodiment. In particular, the above-described embodiment relates to a so-called single structure thin film solar cell, and the present invention is applicable to a structure in which a plurality of unit cells are separated and a plurality of unit cells are connected in series when the facing substrate is applied. It is also applicable to a so-called tandem structure in which a semiconductor layer is composed of two layers with a buffer layer interposed therebetween.

100: substrate 200: light scattering film
220: Bead 240: Binder
222: core portion 224: skin portion
300: front electrode layer 400: semiconductor layer
500: transparent conductive layer 600: rear electrode layer

Claims (18)

Board;
A light scattering film formed on the substrate and including a bead and a binder to fix the bead;
A front electrode layer formed on the light scattering film, the surface of which has a concave-convex structure;
A semiconductor layer formed on the front electrode layer; And
It comprises a back electrode layer formed on the semiconductor layer,
The uneven structure is formed on one surface of the front electrode layer in contact with the semiconductor layer and the thin film type solar cell, characterized in that not formed on the other surface of the front electrode layer in contact with the light scattering film. delete delete delete The method of claim 1,
The bead is a thin film solar cell, characterized in that consisting of a core portion and a skin portion surrounding the core portion. The method of claim 1,
The binder is in contact with the substrate and the front electrode layer, the binder in contact with the substrate and the front electrode layer is a thin film type solar cell, characterized in that the refractive index is different from the substrate and the front electrode layer. The method of claim 1,
Thin film solar cell, characterized in that the transparent conductive layer is further formed under the back electrode layer. The method of claim 1,
The semiconductor layer is a thin film solar cell comprising a first semiconductor layer and a second semiconductor layer configured with a buffer layer interposed therebetween. The method of claim 1,
The bead is in contact with the substrate and the front electrode layer, the bead in contact with the substrate and the front electrode layer is a thin film type solar cell, characterized in that the refractive index is different from the substrate and the front electrode layer. Forming a light scattering film comprising a bead on the substrate and a binder to fix the bead;
Forming a front electrode layer having a concave-convex structure on a surface of the light scattering film;
Forming a semiconductor layer on the front electrode layer; And
Forming a back electrode layer on the semiconductor layer;
And the concave-convex structure is formed on one surface of the front electrode layer in contact with the semiconductor layer and is not formed on the other surface of the front electrode layer in contact with the light scattering film. delete delete delete The method of claim 10,
The bead is made of a thin film solar cell, characterized in that consisting of a core portion and a skin portion surrounding the core portion. The method of claim 10,
And the binder is in contact with the substrate and the front electrode layer, and the binder is in contact with the substrate and the front electrode layer and the refractive index is different from that of the substrate and the front electrode layer. The method of claim 10,
The method of manufacturing a thin film solar cell further comprising a transparent conductive layer forming process before the back electrode layer forming process. The method of claim 10,
The semiconductor layer is a method of manufacturing a thin-film solar cell, characterized in that it comprises a first semiconductor layer and a second semiconductor layer configured with a buffer layer interposed therebetween. The method of claim 10,
The bead is in contact with the substrate and the front electrode layer, the bead in contact with the substrate and the front electrode layer is a method of manufacturing a thin film solar cell, characterized in that the refractive index is different from the substrate and the front electrode layer.

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