KR101474488B1 - Back substrate of compound thin film solar cell and Compound thin film solar cell comprising the same - Google Patents

Abstract

The present invention discloses a rear substrate for a compound thin film solar cell and a compound thin film solar cell comprising the same. A rear substrate for a compound thin-film solar cell according to the present invention is a rear substrate of a compound thin-film solar cell, wherein the rear substrate has a surface modified layer formed by surface treatment on the top surface, and a content of oxygen in the surface modified layer is 14at % Or less, and a nitrogen content of 6.5 at% or more.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor thin film solar cell,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound thin film solar cell, and more particularly, to a compound thin film solar cell having improved rear surface electrode layer for a compound thin film solar cell, It is about solar cells.

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 .

SUMMARY OF THE INVENTION The present invention has been made 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 compound thin film solar cell capable of improving the peel strength characteristics of the substrate and the back electrode by improving the surface modification layer of the rear substrate, A rear substrate for a thin film solar cell and a compound thin film solar cell including the same.

According to an aspect of the present invention, there is provided a back substrate for a compound thin-film solar cell, the back substrate including a surface modification layer formed on a top surface thereof, Layer has a content of oxygen of 14 at% or less and a content of nitrogen of 6.5 at% or more.

Preferably, the rear substrate is made of polyimide.

Preferably, the content of oxygen in the surface modification layer of the rear substrate is 5 at% to 14 at%.

Preferably, the surface modification layer of the rear substrate has a nitrogen content of 6.5 at% to 30 at%.

Preferably, the surface modification layer of the rear substrate is formed by a surface treatment using a plasma treatment, a corona treatment, or a wet method.

Preferably, a rear electrode is formed on the surface modification layer of the rear substrate.

Preferably, the rear electrode is formed using a sputtering method.

Preferably, the rear electrode is one selected from the group consisting of Mo, Ni, Co, Au, Pt, Pd, Ti, Zr, Hf, V, Nb, Ta and W or two or more alloys.

Preferably, the heat-resistant adhesive force between the rear substrate and the rear electrode is 0.200 kgf / cm or more after being left at a temperature of 450 DEG C for 1 hour.

The above technical object can be achieved by a compound thin film solar cell comprising a rear substrate for a compound thin film solar cell according to the present invention. In this case, a Si-based, CI (G) S-based, CI (G) SS-based, CdTe-based or GaAs-based one further including a back electrode, a light absorbing layer, a buffer layer, a window layer and a front electrode laminated on the rear substrate And may be any one selected from a compound thin film solar cell.

According to the present invention, by optimizing the content ratio of oxygen and nitrogen in the surface modification layer of the rear substrate, which is applied to the compound thin-film solar cell, the heat-resistant adhesion between the substrate and the back electrode is improved, It is possible to suppress the peeling phenomenon that may occur in the post-process, thereby improving the efficiency and stability of the compound 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 the structure of a compound thin film solar cell according to the present invention.
FIG. 2 is a view illustrating the structure of a rear substrate for a compound thin film solar cell of FIG. 1. FIG.

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.

FIG. 1 is a cross-sectional view schematically showing the structure of a compound thin-film solar cell according to the present invention, and FIG. 2 is a diagram illustrating a structure of a rear substrate for a compound thin-film solar battery of FIG.

1, a compound thin film solar cell according to the present invention includes a rear substrate 100, a rear electrode 200, a light absorbing layer 300, a buffer layer 400, a window layer 500, and a front electrode 600 Sequentially formed.

The compound thin film solar cell according to the present invention may be a silicon solar cell, a CIGS solar cell, a dye-sensitized solar cell, or an organic solar cell made of a Si-based, CI (G) S-based, CdTe- , A thin-film solar cell, and a flexible solar cell.

As shown in FIG. 2, the rear substrate 100 according to the present invention includes a surface modification layer 110 formed by surface treatment on an upper surface thereof.

The rear substrate 100 is preferably a polymer substrate using polyimide so as to have a flexible characteristic. However, the present invention is not limited thereto, and it is obvious that a glass or metal substrate which can be a base of the lamination structure of solar cells can be used in addition to the polymer substrate. For example, a substrate using sodalime glass as an insulating glass substrate, a ceramic substrate such as alumina, stainless steel (STS), and a flexible polymer may be used.

In the present invention, in the result of composition analysis for the surface modification layer 110 formed on the upper surface by the surface treatment, the content of oxygen is 14 at% or less and the content of nitrogen is 6.5 at% or less in the rear substrate 100 Respectively. More preferably, the rear substrate 100 has an oxygen content of 5 at% to 14 at% and a nitrogen content of 6.5 at% to 30 at% in the surface modification layer 110. If the surface modification layer 110 is formed on the upper surface of the rear substrate 100, the initial adhesion between the surface modification layer 110 and the rear electrode 200 made of a metallic material may be improved. However, The heat-resistant adhesion force after the post-treatment such as the high-temperature treatment may be lowered. This is because the rear electrode 200 is oxidized by the oxygen contained in the surface modification layer 110 to weaken the chemical bonding force with the rear substrate 100. That is, the type and surface state of the constituent components of the surface modification layer 110 after the surface treatment of the rear substrate 100 are closely related to the heat-resistant adhesion force. However, as in the present invention, When the nitrogen content is set within the above-described range, it is possible to obtain an optimal rear substrate 100 that can secure both the initial adhesion with the rear electrode 200 and the heat-resistant adhesion after the high-temperature treatment. Accordingly, the heat-resistant adhesion force between the rear substrate 100 and the rear electrode 200 after leaving for one hour at a temperature of 450 ° C can be formed to be 0.200 kgf / cm or more.

As described above, since the oxygen content in the surface modification layer 110 of the rear substrate 100 is 14 at% or less and the nitrogen content is 6.5 at% or more, the initial adhesion with the back electrode 200 It is possible to secure the heat-resistant adhesion force after the high-temperature treatment and to improve the peeling property of the thin film solar cell.

The surface modification layer 110 of the rear substrate 100 may be formed using a plasma process, a corona process, or a wet process.

The rear electrode 200 may be formed by a sputtering method using a metal selected from Mo, Ni, Co, Au, Pt, Pd, Ti, Zr, Hf, V, Nb, Ta, And then depositing it on the substrate 100 by the method of FIG. Among them, Mo (molybdenum) is a conductive metal layer and has high electrical conductivity, ohmic contact with the light absorption layer 300, and high temperature stability in an atmosphere of selenium (Se) .

The light absorption layer 300 absorbs sunlight to generate an electromotive force. The light absorption layer 300 may be formed of a material such as Si, CI (G) S, CI (G) SS, CdTe or GaAs by a sputtering method, May be formed using an evaporation or printing method. At this time, depending on the material of the light absorption layer 300, the type of the solar cell is determined to be one of a silicon-based solar cell, a CIGS-based solar cell, a dye-sensitized solar cell, or an organic solar cell.

The buffer layer 400 is an n-type semiconductor layer which is pn-junctioned with the light absorption layer 300, which is a p-type semiconductor layer, and ZnS or CdS is formed using CBD (chemical bath deposition) or CSD (chemical surface deposition) .

The window layer 500 is a transparent electrode layer, and any one of ZnO, AZO, SnO ₂ , and ITO may be formed by a sputtering method. At this time, on the upper surface of the window layer 500, a front electrode 600, which is a metal layer made of a metal such as aluminum or nickel, is formed to effectively collect the charge.

Hereinafter, the present invention will be described in detail with reference to examples and comparative examples. However, the embodiments 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 embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example  And Comparative Example

Table 1 below shows preferred examples (1 to 2) of the oxygen and nitrogen content of the surface-modified layer by surface treatment of the rear substrate for a compound thin-film solar cell according to the present invention and comparative examples (1 to 2) The measurement of the peel strength after the initial and heat treatment and the energy conversion efficiency were measured and the results are shown.

Rear substrate Rear electrode evaluation Kinds
thickness
(탆) Content (at%) metal
thickness
(Nm) Peel strength (kgf / cm) Development
efficiency Oxygen nitrogen Early Heat resistance Example 1 PI 50 13.1 7.0 Mo 400 0.693 0.258 14.1% Example 2 PI 50 13.9 6.8 Mo 400 0.689 0.218 14.3% Comparative Example 1 PI 50 16.7 5.9 Mo 400 0.714 0.140 13.7% Comparative Example 2 PI 50 16.0 6.3 Mo 400 0.692 0.167 14.0%

In Examples (1) and (2) and Comparative Examples (1) and (2) of the present invention, a polyimide substrate having a thickness of 50 탆 was prepared. Subsequently, the prepared polyimide substrate was placed in a vacuum chamber to perform plasma surface treatment, and a plasma-treated polyimide substrate was placed in a sputtering chamber. Using molybdenum (Mo) as a target material, A rear electrode was formed on a polyimide substrate having a content ratio. Here, the thickness of the back electrode was measured using KLA Tencor Alpha-step IQ, and the content of the rear substrate was measured using ESCA 2000 XPS manufactured by VG Microtech.

Examples Comparative example  Peel strength measurement and energy conversion efficiency test

A metal layer was formed on the back electrode of polyimide substrate samples having oxygen and nitrogen contents according to Examples (1) to (2) and Comparative Examples (1) and (2) to prepare samples for peel strength measurement. The fabricated samples were allowed to stand at 450 DEG C for 1 hour using a vacuum oven, and then subjected to measurement using a UTM (Model 3342 Universal Testing Machine manufactured by INSTRON) and a Miniature 90 Degree Peel Fixture of INSTRON The peel strength was measured. The peeling strength was measured before and after the heat treatment. The results are shown in Table 1 above.

Further, a light absorbing layer made of a CIGS-based material was formed on polyimide substrate samples having oxygen and nitrogen contents according to Examples (1) and (2) and Comparative Examples (1) and . The power generation efficiency was measured using Wacom's WPSS-1.5 × 1.2-50 × 4 and AM1.5G Solar Simulator. The results are shown in Table 1 above.

Referring to Table 1, in Examples 1 and 2 of the present invention, all the power generation efficiencies were at least 14%, the initial peel strengths were 0.693 kgf / cm and 0.689 kgf / cm, and the heat peel strength after heat treatment Of 0.258 kgf / cm and 0.218 kgf / cm of 0.200 kgf / cm or more.

On the other hand, in Comparative Examples 1 and 2, the power generation efficiency was relatively good at 13% or more, and the initial peel strength was also good at 0.714 kgf / cm and 0.692 kgf / cm, but the heat peel strength after heat treatment was 0.140 kgf / Cm and 0.167 kgf / cm and the peel strength dropped to 0.200 kgf / cm or less.

As described above, in the present invention, by optimizing the oxygen and nitrogen content of the surface modification layer by surface treatment of the rear substrate for a compound thin film solar cell, the degradation of the rear electrode formed on the rear substrate is minimized, The heat-resistant adhesive force can be secured at the same time, so that the efficiency and stability of the compound thin-film solar cell can be improved.

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 110: surface modification layer
200: rear electrode 300: light absorbing layer
400: buffer layer 500: window layer
600: front electrode

Claims (12)

In a rear substrate of a compound thin film solar cell,
Wherein the rear substrate comprises:
A surface modified layer is formed on the upper surface by a surface treatment using a plasma treatment, a corona treatment or a wet method,
Wherein the surface modification layer contains at least oxygen and nitrogen, the oxygen content is 14 at% or less, and the nitrogen content is at least 6.5 at%. The method according to claim 1,
Wherein the rear substrate is made of a polyimide material. The method according to claim 1,
Wherein the surface modification layer of the rear substrate has an oxygen content of 5 at% to 14 at%. The method according to claim 1,
Wherein the surface modification layer of the rear substrate has a nitrogen content of 6.5 at% to 30 at%. The method according to claim 1,
Wherein the surface modification layer of the rear substrate is formed by a surface treatment using a plasma treatment, a corona treatment, or a wet method. The method according to claim 1,
And a rear electrode is formed on the surface modification layer of the rear substrate. The method according to claim 6,
Wherein the back electrode is formed using a sputtering method. The method according to claim 6,
Wherein the back electrode is one selected from the group consisting of Mo, Ni, Co, Au, Pt, Pd, Ti, Zr, Hf, V, Nb, Ta and W or two or more alloys. The method according to claim 6,
Wherein a heat-resistant adhesive force between the rear substrate and the rear electrode is at least 0.200 kgf / cm after standing for one hour at a temperature of 450 ° C. A compound thin film solar cell comprising a rear substrate for a compound thin film solar cell according to any one of claims 1 to 9. 11. The method of claim 10,
Further comprising a back electrode, a light absorption layer, a buffer layer, a window layer, and a front electrode laminated on the rear substrate. 11. The method of claim 10,
Wherein the compound thin film solar cell is any one selected from the group consisting of Si, CI (G) S, CI (G) SS, CdTe, and GaAs.

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