KR20140110149A - Thin film solar cell and Method of fabricating the same - Google Patents

Abstract

The present invention discloses a thin film solar cell and a manufacturing method thereof. A thin film solar cell according to the present invention includes: a substrate; A rear electrode layer formed on the substrate; A light absorbing layer formed on the rear electrode layer; And an adhesive layer formed between the substrate and the rear electrode layer, wherein a ratio (ρ _p / ρ _t ) of an actual density (ρ _p ) to a theoretical density (ρ _t ) of the adhesive layer is at least 0.5.

Description

[0001] The present invention relates to a thin film solar cell and a manufacturing method thereof,

The present invention relates to a thin film solar cell and a manufacturing method thereof, and more particularly, to a thin film solar cell having improved peel strength characteristics by inserting an adhesive layer for improving adhesion between a substrate and a back electrode layer applied to a thin film solar cell, .

With the recent depletion of existing energy resources such as oil and coal, interest in alternative energy to replace them is increasing. Among them, solar cells are attracting particular attention because they have abundant energy resources and there is no problem about environmental pollution. Solar cells include solar power generation that generates the steam needed to rotate the turbine using solar heat and solar cells that convert sunlight (photons) into electrical energy using the properties of semiconductors. (Hereinafter referred to as a "photovoltaic cell").

 Such solar cells are classified into silicon-based solar cells and compound semiconductor solar cells, such as poly-crystal and single-crystal silicon solar cells or amorphous silicon solar cells, depending on raw materials.

As one of the compound semiconductor solar cells, the CIGS solar cell has a structure in which a light absorption layer having a high light absorption coefficient, which is made of an element such as copper (Cu), indium (In), gallium (Ga), selenium (Se) The present invention relates to a solar cell capable of producing a high efficiency solar cell even with a thin film and capable of forming an ideal optical absorption layer with excellent electrical and optical stability, , And many studies have been made with high efficiency solar cell materials.

Molybdenum (Mo), which has high melting point, low ohmic contact, and high stability against high temperature in a selenium (Se) atmosphere, is mainly used for the back electrode layer of such a thin film solar cell.

However, mismatching occurs due to the difference in thermal expansion coefficient between the rear electrode layer made of molybdenum and the substrate. This leads to a reduction in the bonding force at the contact interface between the back electrode layer and the substrate, and eventually the back electrode layer peels off the surface of the substrate, resulting in peeling. As a result, the efficiency and stability may deteriorate .

Disclosure of Invention Technical Problem [8] The present invention has been devised in order to solve the problems of the prior art as described above, and it is an object of the present invention to provide a solar cell module in which an adhesive layer for improving adhesion is inserted between a substrate and a back electrode layer, To improve the efficiency and stability of a solar cell, and a method of manufacturing the same.

According to an aspect of the present invention, there is provided a thin film solar cell comprising: a substrate; A rear electrode layer formed on the substrate; A light absorbing layer formed on the rear electrode layer; And an adhesive layer formed between the substrate and the rear electrode layer, wherein a ratio (ρ _p / ρ _t ) of an actual density (ρ _p ) to a theoretical density (ρ _t ) of the adhesive layer is at least 0.5.

Preferably, the adhesive layer is at least one selected from the group consisting of nickel (Ni), chromium (Cr), cobalt (Co), and molybdenum (Mo)

Preferably, the adhesive layer has a thickness of 5 to 100 nm.

Preferably, the adhesive layer is formed using a sputtering method.

Preferably, the substrate is further provided with an uneven layer by plasma surface treatment.

Preferably, the roughness layer of the substrate has an average roughness Rz of 5 to 20 nm.

Preferably, the rear electrode layer is made of molybdenum (Mo).

Preferably, the light absorbing layer includes a CIGS-based compound layer containing copper (Cu), indium (In), gallium (Ga), and selenium (Se).

Preferably, the light emitting device further includes a buffer layer, a window layer, and a front electrode layer formed on the light absorbing layer.

According to an aspect of the present invention, there is provided a method of manufacturing a thin film solar cell, including: (a) forming an adhesive layer on a substrate; (b) forming a rear electrode layer on the adhesive layer; And (c) forming a light absorption layer on the rear electrode layer, wherein the ratio ( _{p / rt} ) of the actual density (rho _p ) of the adhesive layer to the theoretical density (rho _t ) .

Preferably, in the step (a), the adhesive layer is at least one selected from the group consisting of nickel (Ni), chromium (Cr), cobalt (Co), and molybdenum (Mo).

Preferably, in the step (a), the adhesive layer has a thickness of 5 to 100 nm.

Preferably, in the step (a), the adhesive layer is formed by a sputtering method.

Preferably, the step (a) further comprises forming an uneven layer using a plasma surface treatment on the substrate before the step (a).

Preferably, the roughness layer of the substrate has an average roughness Rz of 5 to 20 nm.

Preferably, in the step (b), the rear electrode layer is made of molybdenum (Mo).

Preferably, in the step (c), the light absorbing layer includes a CIGS compound layer containing copper (Cu), indium (In), gallium (Ga), and selenium (Se).

Preferably, the step (c) further comprises forming a buffer layer, a window layer and a front electrode layer on the light absorption layer.

According to the present invention, an initial adhesion between a substrate and a rear electrode layer is improved by inserting an adhesive layer for improving adhesion between a substrate and a rear electrode layer applied to a thin film solar cell and optimizing physical properties of the adhesive layer, It is possible to suppress a peeling phenomenon that may occur in a subsequent process such as a high temperature treatment in an atmosphere, thereby improving the efficiency and stability of the thin film solar cell.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and, together with the description, And shall not be interpreted.
1 is a cross-sectional view schematically showing a structure of a thin film solar cell according to the present invention.
FIGS. 2 to 4 are process sectional views sequentially illustrating a method of manufacturing a thin film solar cell according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be interpreted in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in this specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

1 is a cross-sectional view schematically showing a structure of a thin film solar cell according to the present invention.

1, a thin film solar cell according to the present invention includes a substrate 100, an adhesive layer 200, a rear electrode layer 300, and a light absorbing layer 400. The thin film solar cell may further include a buffer layer 500, a window layer 600, and a front electrode layer 700 on the light absorption layer 400.

A polymer substrate using polyimide may be used as the substrate 100 so as to have a flexible characteristic. However, the present invention is not limited thereto, and it is apparent that various materials that can be a basis of the laminated structure of the solar cell can be used in addition to the polymer substrate. For example, a substrate using sodalime glass as an insulating glass substrate can be used.

Meanwhile, the substrate 100 may be formed with a roughness layer (not shown) having a predetermined roughness by removing a part of the surface of the substrate 100 with the removal of contaminants on the surface thereof by the plasma surface treatment in the pretreatment process. In this case, the substrate 100 preferably has an average roughness Rz of 5 to 20 nm.

The adhesive layer 200 is a metal conductor layer for improving adhesion between the substrate 100 and the rear electrode layer 300. The adhesive layer 200 may be formed of one selected from the group consisting of nickel (Ni), chrome (Cr), cobalt (Co), and molybdenum Or two or more alloys. The adhesive layer 200 may be formed using a sputtering method. At this time, the adhesive layer 200 preferably has a thickness T of 5 to 100 nm.

In the present invention, the sputtering current density is controlled in the step of forming the adhesive layer 200 so that the ratio (ρ _p / ρ _t ) of the actual density (ρ _p ) to the theoretical density (ρ _t ) of the adhesive layer (200) . This is because when the adhesive layer 200 is formed by the sputtering method, the theoretical density (ρ _t ) inherent to the metal constituting the adhesive layer 200 is lowered by the deformation of the process such as lattice defects or voids in the sputtering process Thus, the difference between the actual density (rho _p ) and the theoretical density (rho _t ) is inevitable. The ratio (rho _p / rho _t ) of the actual density (rho _p ) of the adhesive layer (200) to the theoretical density (rho _t ) serves as an element that affects the adhesion force contributed by the adhesive layer (200).

That is, in the formation of the adhesive layer 200, the most preferable case is when the ratio (ρ _p / ρ _t ) between the actual density ρ _p and the theoretical density ρ _t of the adhesive layer 200 is 1, 200 are densely formed without gaps, but it is difficult to realize this in the process of sputtering.

Therefore, the present invention is characterized in that the ratio (ρ _p / ρ _t ) between the actual density (ρ _p ) and the theoretical density (ρ _t ) of the adhesive layer (200) is at least 0.5 or more. This is because the adhesive force of at least 0.5 when the ratio is more than (ρ _p / ρ _t) of the measured density (ρ _p) and the theoretical density (ρ _t) of the adhesive layer 200 is not reduced. If the measured density (ρ _p) and the theoretical density (ρ _t) of the ratio (ρ _p / ρ _t) of 0.5 is less than the case, a level gap the adhesive layer 200 and the substrate of affecting the adhesiveness of the adhesive layer 200 Which may occur at the interface of the substrate 100.

The substrate 100 and the rear electrode layer 300 may be formed in such a manner that the ratio (ρ _p / ρ _t ) of the actual density ρ _p and the theoretical density ρ _t of the adhesive layer 200 is at least 0.5, The initial adhesion between the substrate 100 and the rear electrode layer 200 can be improved and the peeling phenomenon that may occur in a subsequent process such as high temperature treatment in a selenium (Se) atmosphere can be prevented It is possible to improve the efficiency and stability of the thin film solar cell.

The rear electrode layer 300 may be made of molybdenum (Mo) having high electrical conductivity, ohmic contact with the light absorption layer 400, and high temperature stability under selenium (Se) atmosphere. The rear electrode layer 300 may be formed using a sputtering method.

The light absorption layer 400 absorbs sunlight to generate an electromotive force, and is formed of a CIGS-based material. CIGS is an increase of efficiency by doping gallium (Ga) element into CuInSe ₂ (CIS) three-element semiconductor made of copper (Cu), indium (In) and selenium (Se).

The buffer layer 500 is an n-type semiconductor layer pn-junctioned with the light absorption layer 400, which is a p-type semiconductor layer, and is formed of cadmium sulfide (Cds).

The window layer 600 may be formed of any one of ITO, ZnO, and i-ZnO as a transparent electrode layer. At this time, a front electrode layer 700, which is a metal layer made of a metal such as aluminum (Al) or nickel (Ni), is formed on the upper surface of the window layer 600 to effectively collect charge.

As described above, the thin film solar cell according to the present invention has a structure in which the adhesive layer 200 is inserted between the substrate 100 and the rear electrode layer 300 and the physical properties of the adhesive layer 200, that is, the actual density of the adhesive layer 200 the initial adhesion between the substrate 100 and the back electrode layer 200 is improved by forming the ratio p _p / _{t t} of the selenium ( _p ) and the theoretical density ( _{t p} ) It is possible to suppress a peeling phenomenon that may occur in a subsequent process such as a high temperature treatment in an atmosphere of Se, thereby improving the efficiency and stability of the thin film solar cell.

FIGS. 2 to 4 are process sectional views sequentially illustrating a method of manufacturing a thin film solar cell according to the present invention.

2 to 4, a method of manufacturing a thin film solar cell according to the present invention includes:

A step of forming an adhesive layer 200 on the substrate 100 and a step of forming a rear electrode layer 300 on the adhesive layer 200 and a step of forming a light absorbing layer 400 on the rear electrode layer 300 . The thin film solar cell manufacturing method may further include forming a buffer layer 500, a window layer 600, and a front electrode layer 700 on the light absorption layer 400.

First, as shown in FIG. 2, a substrate 100 is prepared, and an adhesive layer 200 is formed on the substrate 100. The adhesive layer 200 is a metal conductor layer for improving adhesion between the substrate 100 and the rear electrode layer 300. The adhesive layer 200 may be formed of one selected from the group consisting of nickel (Ni), chrome (Cr), cobalt (Co), and molybdenum Or two or more alloys. The adhesive layer 200 may be formed using a sputtering method. At this time, the adhesive layer 200 preferably has a thickness T of 5 to 100 nm.

In the present invention, the sputtering current density is controlled in the step of forming the adhesive layer 200 so that the ratio (ρ _p / ρ _t ) of the actual density (ρ _p ) to the theoretical density (ρ _t ) of the adhesive layer (200) . This is because the adhesive force of at least 0.5 when the ratio is more than (ρ _p / ρ _t) of the measured density (ρ _p) and the theoretical density (ρ _t) of the adhesive layer 200 is not reduced. If the measured density (ρ _p) and the theoretical density (ρ _t) of the ratio (ρ _p / ρ _t) of 0.5 is less than the case, a level gap the adhesive layer 200 and the substrate of affecting the adhesiveness of the adhesive layer 200 Which may occur at the interface of the substrate 100.

Then, as shown in FIG. 3, a rear electrode layer 300 is formed on the adhesive layer 200. The target material of the sputtering may be formed of molybdenum (Mo), which is a material for forming the rear electrode layer 300, in the forming material of the adhesive layer 200, and may be formed by sputtering. The process is performed.

Then, as shown in FIG. 4, a light absorption layer 400 is formed on the rear electrode layer 300. Although not shown in the drawing, a buffer layer 500, a window layer 600, and a front electrode layer 700 are sequentially stacked on the light absorption layer 400 to complete a thin film solar cell.

As described above, according to the method of manufacturing a thin film solar cell according to the present invention, the ratio (rho _p / rho _t ) of the actual density (rho _p ) and the theoretical density (rho _t ) of the adhesive layer (200) It is possible to improve the initial adhesion between the substrate 100 and the rear electrode layer 200 and to suppress the peeling phenomenon that may occur in a subsequent process such as high temperature treatment in a selenium (Se) atmosphere, The efficiency and stability of the battery can be improved.

To explain the present invention concretely, the relationship between the ratio (? _P /? _T ) between the actual density (? _P ) of the adhesive layer (200) and the theoretical density (? _T ) . However, the experimental example according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the experiment examples described below. Experimental examples of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Experimental Example

First, a polyimide substrate was prepared. Subsequently, the prepared polyimide substrate was placed in a sputtering chamber, and a nickel-chromium (N-Cr) alloy was used as a target material, and an adhesive layer was formed to a thickness of 20 nm while maintaining a process pressure of 3 mTorr. At this time, four specimens having the ratio (ρ _p / ρ _t ) between the actual density (ρ _p ) and the theoretical density (ρ _t ) as shown in Table 1 below were prepared by controlling the sputtering current density. Here, the actual density ( _p ) of the adhesive layer was measured using a RBS (Rutherford Backscattering Spectrometry) analyzer.

In the experimental example  Relationship between the adhesion of the sample and

The four samples prepared according to the Experimental Example were heated at 400 DEG C for 30 minutes and then adhered with a width of 1 nm using a universal testing machine (UTM). The results are shown in Table 1 below Respectively.

ρ _p / ρ _t Adhesion (kN / m) Experimental Example 1 0.4 0.56 Experimental Example 2 0.6 0.62 Experimental Example 3 0.7 0.64 Experimental Example 4 0.8 0.64

Referring to Table 1, it can be seen that the adhesion of the sample prepared according to the experimental example is closely related to the ratio (ρ _p / ρ _t ) between the actual density (ρ _p ) of the adhesive layer and the theoretical density (ρ _t ) in particular, the measured density (ρ _p) and the theoretical density (ρ _t) of the adhesive ratio (ρ _p / ρ _t) is 0.5 or less experiment 1 than 0.5 or more test example 2 to example 4 seen that the adhesive strength is good in .

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be understood that various modifications and changes may be made without departing from the scope of the appended claims.

100: substrate 200: adhesive layer
300: rear electrode layer 400: light absorbing layer
500: buffer layer 600: window layer
700: front electrode layer

Claims (18)

Board;
A rear electrode layer formed on the substrate;
A light absorbing layer formed on the rear electrode layer; And
And an adhesive layer formed between the substrate and the rear electrode layer,
Wherein a ratio ( _p / _t ) of an actual density (rho _p ) of the adhesive layer to a theoretical density (rho _t ) is at least 0.5 or more. The method according to claim 1,
Wherein the adhesive layer is at least one selected from the group consisting of nickel (Ni), chromium (Cr), cobalt (Co), and molybdenum (Mo). The method according to claim 1,
Wherein the adhesive layer has a thickness of 5 to 100 nm. The method according to claim 1,
Wherein the adhesive layer is formed by a sputtering method. The method according to claim 1,
Wherein the substrate is further formed with an uneven layer by plasma surface treatment. 6. The method of claim 5,
Wherein the uneven layer of the substrate has an average roughness (Rz) of 5 to 20 nm. The method according to claim 1,
Wherein the back electrode layer is made of molybdenum (Mo). The method according to claim 1,
Wherein the light absorption layer comprises a CIGS compound layer containing copper (Cu), indium (In), gallium (Ga) and selenium (Se). The method according to claim 1,
And a buffer layer, a window layer, and a front electrode layer formed on the light absorption layer. (a) forming an adhesive layer on top of a substrate;
(b) forming a rear electrode layer on the adhesive layer; And
(c) forming a light absorption layer on the rear electrode layer,
Wherein the ratio (? _{P /} ? _T ) of the actual density (? _P ) of the adhesive layer to the theoretical density (? _T ) is at least 0.5 or more. 11. The method of claim 10,
Wherein the adhesive layer is one or more selected from the group consisting of nickel (Ni), chrome (Cr), cobalt (Co), and molybdenum (Mo) in the step (a). 11. The method of claim 10,
In the step (a), the adhesive layer has a thickness of 5 to 100 nm. 11. The method of claim 10,
Wherein the step (a) comprises forming the adhesive layer using a sputtering method. 11. The method of claim 10,
The method of claim 1, further comprising forming an uneven layer on the upper surface of the substrate using the plasma surface treatment before the step (a). 15. The method of claim 14,
Wherein the uneven layer of the substrate has an average roughness (Rz) of 5 to 20 nm. 11. The method of claim 10,
In the step (b), the rear electrode layer is made of molybdenum (Mo). 11. The method of claim 10,
Wherein the light absorption layer comprises a CIGS compound layer containing copper (Cu), indium (In), gallium (Ga), and selenium (Se) in the step (c). 11. The method of claim 10,
Forming a buffer layer, a window layer, and a front electrode layer on the light absorption layer after the step (c).

Images