Solar cell and method for manufacturing same

Disclosed is a solar cell including a support substrate, a barrier layer on the support substrate, and a photo-electro conversion part on the barrier layer. The barrier layer comprises first and second barrier layers having porosities different from each other.

TECHNICAL FIELD

The embodiment relates to a solar cell and a method for manufacturing the same.

BACKGROUND ART

Recently, as the demand for energy is increased, researches and studies on solar cells to convert solar energy into electrical energy have been actively carried out.

The solar cells may be classified into silicon-based solar cells, non-silicon-based solar cells, and dye-sensitized solar cells. Among them, the non-silicon-based solar cells may have the form of a thin film to reduce the loss of material while widening the use range of the solar cells. In addition, a light absorbing layer used in the silicon-based solar cells is less degraded by a light to represent a long life span.

In order to realize flexible solar cells, the technology to employ a support substrate made of metallic material has been applied.

DISCLOSURE OF THE INVENTION

Technical Problem

The embodiment provides a solar cell and a method for manufacturing the same, capable of preventing impurities from diffusing from a photo-electro conversion part to a support substrate, and preventing the de-lamination between the support substrate and the photo-electro conversion part.

Technical Solution

According to the embodiment, there is provided a solar cell including a support substrate, a barrier layer on the support substrate, and a photo-electro conversion part on the barrier layer, wherein the barrier layer includes first and second barrier layers having porosities different from each other.

According to the embodiment, there is provided a method for manufacturing a solar cell. The method includes forming a first barrier layer on a support substrate, forming a second barrier layer, which has a porosity different from a porosity of the first barrier layer, on the first barrier layer, and forming a photo-electro conversion part on the second barrier layer.

Advantageous Effects

As described above, according to the solar cell of the embodiment, the first barrier layer having a denser structure is formed in adjacent to the support substrate, and the second barrier layer having a less dense structure is formed in adjacent to the photo-electro conversion part. Therefore, the first barrier layer can prevent the impurities generated when manufacturing the solar cell from diffusing to the photo-electro conversion part.

In addition, the second barrier layer having a porous structure increases the contact area with the photo-electro conversion part, thereby not only effectively preventing the delamination between the support substrate and the photo-electro conversion part, but improving the photo-electro conversion efficiency.

In addition, in the method for manufacturing the solar cell according to the embodiment, the first and second barrier layers can be formed by changing only a simple process condition using the same material. Therefore, the manufacturing cost of the solar cell according to the embodiment can be reduced.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the embodiment will be described in detail with reference to accompanying drawings so that those skilled in the art can easily realize the embodiment.

FIGS. 1 and 2are sectional views schematically showing the solar cell according to the embodiment.

Referring toFIG. 1, a solar cell100according to the embodiment includes a support substrate10, a barrier layer20on the support substrate10, and a photo-electro conversion part30on the barrier layer20. In addition, the solar cell100according to the embodiment further includes a metallic layer40on the support substrate10as shown inFIG. 2.

The support substrate10has the shape of a plate, and supports the barrier layer20and the photo-electro conversion part30.

The support substrate10may include a rigid substrate or a flexible substrate. In detail, the support substrate120may include a flexible substrate. For example, the support substrate10may include a flexible metallic substrate. Accordingly, the solar cell100can be realized as a flexible solar cell.

The support substrate10may include a solar cell substrate generally used in the art which the present invention pertains to. For example, the support substrate10may include a material selected from the group consisting of iron, lead (Pb), cobalt (Co), nickel (Ni), copper (Cu), tin (Sn), and the combination thereof, but the embodiment is not limited thereto. According to one embodiment, the support substrate10may include stainless steel mainly made of iron.

In addition, the support substrate10may include an insulator such as glass or plastic.

The barrier layer20is provided on the support substrate10. In detail, the barrier layer20is interposed between the support substrate10and the photo-electro conversion part30. The barrier layer20has a thickness of about 5 μm or less, but the embodiment is not limited thereto.

The barrier layer20includes first and second barrier layers22and24. In addition, the first and second barrier layers22and24may directly make contact with each other.

In detail, the barrier layer20includes the first barrier layer22on the support substrate and the second barrier layer24on the first barrier layer22. In other words, the first barrier layer22is adjacent to the support substrate22, and the second barrier layer24is adjacent to the photo-electro conversion layer30.

The first and second barrier layers22and24have porosities different from each other. In more detail, the first barrier layer22adjacent to the support substrate10has smaller porosity, so that the first barrier layer22may be densely formed. In addition, the second barrier layer24adjacent to the photo-electro conversion part30may have the porous structure representing greater porosity.

As described above, the first barrier layer22may have a dense structure, thereby effectively preventing the material of the support substrate10from diffusing to the photo-electro conversion part30. For example, the first barrier layer22can prevent the material of the support substrate10and the impurities on the support substrate10from diffusing to the photo-electro conversion part30in a high-temperature heat treatment process to form the photo-electro conversion part30.

The porosity of the first barrier layer22can represent about 10% or less, but the embodiment is not limited thereto. In detail, the porosity of the first barrier layer22may be about 5%, or about 1% or less of porosity, but the embodiment is not limited thereto.

As described above, the second barrier layer24may have a porous structure representing greater porosity. Accordingly, the contact area between the second barrier layer24and the photo-electro conversion part30may be increased. In addition, the delamination between the second barrier layer24and the photo-electro conversion part30can be effectively prevented, and the surface area of the photo-electro conversion part30is increased, so that the photo-electro conversion efficiency can be improved.

The porosity of the second barrier layer24may be in the range of about 20% to about 40%, but the embodiment is not limited thereto. In detail, the porosity of the second barrier layer24may be in the range of about 30% to about 40%, but the embodiment is not limited thereto.

Meanwhile, although accompanying drawings and the detailed description disclose that the first and second barrier layers22and24constituting the barrier layer20are separately formed from each other, but the embodiment is not limited thereto. In other words, the scope of the present embodiment reaches the case in which the porosity of a portion of the barrier layer20adjacent to the support substrate10is different from the porosity of a portion of the barrier layer20adjacent to the photo-electro conversion part30in the barrier layer20even if the boundary between the first barrier layer22and the second barrier layer24is unclear.

In other words, the solar cell according to the embodiment includes the first barrier layer22, which has the dense structure and is adjacent to the support substrate10, and the second barrier layer24which has the porous structure and is adjacent to the photo-electro conversion part30. Accordingly, the barrier layer20not only can prevent impurity diffusion and the delamination phenomenon, but also can improve the photo-electro conversion efficiency.

The first and second barrier layers22and24may include oxide. In detail, the first and second barrier layers22and24may include metallic oxide. For example, each of the first and second barrier layers22and24may include material selected from the group consisting of aluminum oxide, titanium oxide, magnesium oxide, tungsten oxide, and the combination thereof.

In addition, the first barrier layer22may include only metal, or may include both of the metal and the oxide of the metal. For example, the first barrier layer22may include any material selected from the group consisting of aluminum (Al), titanium (Ti), magnesium (Mg), tungsten (W), the oxide thereof, and the combination thereof.

The barrier layer20including the first and second barrier layers22an24has a thickness of about 5 μm or less, but the embodiment is not limited thereto. As described above, the barrier layer20may include oxide. If the oxide barrier layer20having a thickness exceeding about 5 μm is bent, the oxide barrier layer20may be cracked. Accordingly, the oxide barrier layer20having the thickness exceeding about 5 μm may not be applied to the flexible solar cell100.

The first and second barrier layers22and24may include the same material. In this case, the first and second barrier layers22and24may be formed through a scheme of simply changing only the process conditions using the same material. Therefore, the manufacturing cost of the solar cell according to the embodiment can be reduced. Hereinafter, the method for manufacturing the solar cell will be described in more detail.

The ratio of the thickness of the second barrier layer24to the thickness of the first barrier layer22may be in the range of about 0.1 to about 0.3. If the ratio is 0.3, the second barrier layer24having the porous structure has a thick thickness, and the first barrier layer22has a thin thickness. Therefore, the first barrier layer22may not effectively prevent the diffusion of impurities. In addition, if the ratio is less than 0.1, the second barrier layer24has a thin thickness, so that the contact area may not be sufficiently ensured.

Referring toFIG. 2, according to the solar cell of the embodiment, the metallic layer40may be additionally provided on the substrate10. The metallic layer40may include metal. For example, the metallic layer40may include material selected from the group consisting of Al, Ti, Mg, W, and the combination thereof.

The metallic layer40may be provided to form the barrier layer20. For example, the barrier layer20may be formed by oxidizing the metallic layer40. In this case, as shown inFIG. 1, the metallic layer40may be changed into the barrier layer20by oxidizing the entire portion of the metallic layer40. However, as shown inFIG. 2, only a portion of the metallic layer40is changed into the barrier layer20, and a portion of the metallic layer40, which is not changed into the barrier layer20, may remain on the support substrate10.

The metallic layer40has a very dense structure like the first barrier layer22. Therefore, together with the first barrier layer22, the metallic layer40can effectively prevent the material of the support substrate10from diffusing to the photo-electro conversion part30.

The photo-electro conversion part30is provided on the barrier layer20. In detail, the photo-electro conversion part30is provided on the second barrier layer24. The photo-electro conversion part20converts the solar energy into electrical energy.

The photo-electro conversion part30includes a first electrode layer31, a light absorbing layer33, and a second electrode layer39. The photo-electro conversion part30may further include a buffer layer35and a high-resistance buffer layer37interposed between the light absorbing layer33and the second electrode layer39, but the embodiment is not limited thereto.

The first electrode layer31may include material representing superior electrical characteristics. For example, the first electrode layer31may include molybdenum (Mo), copper (Cu), nickel (Ni), aluminum (Al), and the alloy thereof.

The light absorbing layer33is provided on the first electrode layer31.

The light absorbing layer33may include a non-silicon-based material. In other words, the light absorbing layer33may include a group I-III-IV compound. For example, the light absorbing layer33may include a Cu—In—Ga—Se-based compound (Cu(In,Ga)Se2, CIGS), a Cu—In—Se (CIS) compound, or a Cu—Ga—Se (CGS) compound.

The light absorbing layer33may include a group II-IV compound or a group III-IV compound. For example, the light absorbing layer33may include a Cd—Te compound or a Ga—As compound.

The buffer layer35on the light absorbing layer33can reduce the lattice constant difference and the energy band difference from the second electrode layer29. For example, the light absorbing layer33may include cadmium sulfide (CdS).

The high-resistance buffer layer37on the buffer layer35can prevent the buffer layer35from being damaged when the second electrode layer39is formed. For example, the buffer layer35may include zinc oxide (ZnO).

The second electrode layer39may include a transparent conductive material. In addition, the second electrode layer39may have the characteristic of an N type semiconductor. In this case, the second electrode layer39constitutes an N type semiconductor layer together with the buffer layer35to form PN junction with the light absorbing layer33which serves as a P type semiconductor layer. For example, the second electrode layer39may include Al doped zinc oxide (AZO).

As described above, the solar cell according to the embodiment may include the light absorbing layer33including a CIGS-based compound, a CIS-based compound, a CGS-based compound, a Cd—Te compound or a Ga—As compound. Accordingly, the superior photo-electro conversion efficiency can be represented. Therefore, the solar cell100can have a thin thickness, can reduce the loss of the material, and can be utilized in various industrial fields.

Meanwhile, the present embodiment is not limited thereto. Therefore, the photo-electro conversion part30may include a photo-electro conversion part constituting a dye-sensitized solar cell, an organic solar cell, or a silicon solar cell.

Hereinafter, the method for manufacturing the solar cell according to the embodiment will be described with reference toFIGS. 3 to 6. The method for manufacturing the solar cell according to the preset embodiment will be described by making reference to the above description of the solar cell. The above description of the solar cell will be incorporated in the description of the method for manufacturing the solar cell according to the present embodiment.

FIGS. 3ato 3dare sectional views schematically showing the process steps in the method for manufacturing the solar cell according to the first embodiment.

As shown inFIG. 3a, the first barrier layer22is formed on the support substrate10. The first barrier layer22may include oxide such as Al oxide, Ti oxide, Mg oxide, or W oxide, and may be formed through various schemes. For example, the first barrier layer22may be formed through a process selected from the group consisting of a sputtering process, an electroplating process, a micro-arc oxidation process, an anodizing process, and the combination thereof.

Thereafter, as shown inFIG. 3b, the second barrier layer24is formed on the first barrier layer22with the porosity higher than that of the first barrier layer22.

The second barrier layer24may include oxide such as Al oxide, Ti oxide, Mg oxide, and W oxide, and may be formed through various schemes. For example, the second barrier layer24may be formed through a process selected from the group consisting of a sputtering process, an electroplating process, a micro-arc oxidation process, an anodizing process, and the combination thereof.

The first and second barrier layers22and24may include the same material. In this case, the first and second barrier layers22and24may be formed through a scheme of simply changing only the process conditions under the same process. For example, after the first barrier layer22has been formed through an electroplating process, the second barrier layer24may be formed in a porous structure through a micro-arc oxidation process in which a high-voltage is alternately applied to an anode electrode and a cathode electrode in the same plating bath.

As described above, in the method for manufacturing the solar cell according to the present embodiment, the barrier layer20including layers, which are adjacent to the support substrate10and the photo-electro conversion part30, respectively and have porosities different from each other, can be formed through a simple process.

In order to reduce the roughness of the barrier layer20, a process of polishing the barrier layer20may be further performed. The polishing process may be performed before the photo-conversion part30is formed on the barrier layer20after the barrier layer20has been formed. In addition, the polishing process includes both of a mechanical polishing process and/or a chemical polishing process.

Thereafter, as shown inFIG. 3c, the photo-electro conversion part30is formed on the barrier layer20to manufacture the solar cell100. Hereinafter, the detail thereof will be described.

First, the first electrode layer31is formed on the barrier layer20. For example, the first electrode layer31may be formed by depositing Mo through a sputtering process. In addition, the first electrode layer31may include at least two layers. The layers may include the same metal, or may include different metals. The first electrode layer31including the at least two layers may be formed through two processes having process conditions different from each other.

Next, the light absorbing layer33is formed on the first electrode layer31. The light absorbing layer33may be formed through various schemes. For example, the light absorbing layer33may be formed through an evaporation scheme or a sputtering process.

According to the evaporation scheme, the CIGS-based light absorbing layer33may be formed by simultaneously or separately evaporating Cu, In, Ga, and Se.

According to the sputtering process, after a metallic precursor layer has been formed through the sputtering process, the CIGS-based light absorbing layer33may be formed through the selenization process. In other words, after the metallic precursor layer including Cu, In, and Ga has been formed through the sputtering process using a Cu target, an In target, and a Ga target, the CIGS-based light absorbing layer33may be formed through the selenization process. In addition, the CIGS-based light absorbing layer33may be formed by simultaneously performing the sputtering process and the selenization process.

Although the above method discloses the forming of the CIGS-based light absorbing layer33, a target an evaporation material vary depending on a desired material to form various light absorbing layers.

Thereafter, the buffer layer35may be formed on the light absorbing layer33. The buffer layer35may be formed through a chemical bath deposition (CBD) scheme, a sputtering scheme, an evaporation scheme, or a chemical vapor deposition (CVD) scheme.

The high-resistance buffer layer37is formed on the buffer layer35. For example, the high-resistance buffer layer37may be formed by depositing ZnO. However, the embodiment is not limited thereto, and the high-resistance buffer layer37may be made of various materials through various schemes.

Thereafter, the second electrode layer39is formed on the high-resistance buffer layer37.

FIGS. 4ato 4care sectional views showing the process steps in a method for manufacturing a solar cell according to a second embodiment.

In the method for manufacturing the solar cell according to the second embodiment, the second barrier layer24having higher porosity may be formed by etching the upper portion of a first barrier layer22a. For example, the upper portion of the first barrier layer22amay be etched by using a fluoride etchant to form the second barrier layer24. A portion of the first barrier layer22a, which is not etched, remains as the first barrier layer22. Thereafter, as shown inFIG. 5c, the photo-electro conversion part30is formed on the barrier layer20to manufacture the solar cell100.

As described above, according to the second embodiment, the barrier layer20including the first and second barrier layers22and24may be manufactured through the simple process of etching the first barrier layer. Therefore, the barrier layer20, in which the porosity of a portion adjacent to the support substrate10is different from the porosity of a portion adjacent to the photo-electro conversion part30, can be formed through a simple process.

FIGS. 5 and 6are sectional views showing solar cells manufactured according to third and fourth embodiments.

According to the third and fourth embodiments, the barrier layer20may be formed by oxidizing the metallic layer40after the metallic layer40has been formed on the support substrate10.

The metallic layer40may be formed on the support substrate10through various processes such as a sputtering process and an electroplating process. Next, the metallic layer40is oxidized. In this case, depending on the oxidized degree of the metallic layer40, the metallic layer40remains on the support substrate10as shown inFIG. 2, or the entire portion of the metallic layer40may be changed into two barrier layers as shown inFIG. 1.

Referring toFIG. 5, the Al metallic layer40is formed on the support substrate10through an electroplating process. The upper portion of the Al metallic layer40is oxidized through the micro-arc oxidation process so that the upper portion of the Al metallic layer40can be changed into the barrier layer20. In this case, a portion of the Al metallic layer40may remain on the support substrate10without being oxidized.

FIG. 6is a sectional view showing the metallic layer40and the barrier layer20according to the fourth embodiment. Referring toFIG. 6, the barrier layer20may be formed by anodizing the metallic layer40. In the anodizing process for the metallic layer40, the first and second barrier layers22and24may be simultaneously formed. In detail, the barrier layer20may include the first barrier layer22having a dense structure in adjacent to the support substrate10and the second barrier layer24having a porous structure in adjacent to the photo-electro conversion part30.