KR101081300B1 - Solar cell and method of fabricating the same - Google Patents

Abstract

A solar cell is disclosed. The solar cell is a substrate; A light absorbing layer disposed on the substrate; A buffer layer disposed on the light absorbing layer, the buffer layer comprising a zinc compound; And a window layer disposed on the buffer layer. Zinc compounds are represented by the formula Zn _X A _Y. Wherein A is selected from the group consisting of sulfur, selenium and telenium, where X is greater than 0 and less than 2, and Y is greater than 0 and less than 2.

Solar cell, zinc, telenium, buffer layer

Description

SOLAR CELL AND METHOD OF FABRICATING THE SAME

An embodiment relates to a solar cell and a manufacturing method thereof.

Recently, as the demand for energy increases, development of solar cells for converting solar energy into electrical energy is in progress.

In particular, CIGS-based solar cells that are pn heterojunction devices having a substrate structure including a glass substrate, a metal back electrode layer, a p-type CIGS-based light absorbing layer, a high resistance buffer layer, an n-type window layer, and the like are widely used.

The embodiment has an improved efficiency, to provide a solar cell and a method for manufacturing a solar cell containing no heavy metal, such as cadmium or less.

Solar cell according to one embodiment includes a substrate; A light absorbing layer disposed on the substrate; A buffer layer disposed on the light absorbing layer, the buffer layer comprising a zinc compound; And a window layer disposed on the buffer layer.

According to one or more exemplary embodiments, a method of manufacturing a solar cell includes forming an electrode layer on a substrate; Forming a light absorbing layer on the electrode layer; Forming a buffer layer on the light absorbing layer, wherein the buffer layer comprises a zinc compound represented by the following formula; And forming a window layer on the buffer layer.

Wherein the zinc compound is represented by the formula Zn _X A _Y , A is selected from the group consisting of sulfur, selenium and telenium, X is greater than 0 and less than 2, and Y is greater than 0 and less than 2.

The solar cell according to the embodiment includes a buffer layer including the zinc compound instead of cadmium sulfide. That is, the solar cell according to the embodiment can form a buffer layer without using cadmium.

Therefore, the solar cell according to the embodiment does not contain heavy metals such as cadmium or very few.

Therefore, the solar cell according to the embodiment does not damage the human body and prevents contamination by heavy metals.

In addition, silver or aluminum may be easily doped into the buffer layer including the zinc compound.

Therefore, the solar cell according to the embodiment can easily adjust the bandgap energy of the buffer layer by silver or aluminum, and improve the efficiency.

In the description of the embodiments, it is described that each substrate, film, electrode, groove or layer or the like is formed "on" or "under" of each substrate, electrode, film, groove or layer or the like. In the case, “on” and “under” include both being formed “directly” or “indirectly” through other components. In addition, the upper or lower reference of each component is described with reference to the drawings. The size of each component in the drawings may be exaggerated for the sake of explanation and does not mean the size actually applied.

1 is a cross-sectional view showing a cross section of a solar cell according to an embodiment.

Referring to FIG. 1, the solar cell includes a support substrate 100, a back electrode layer 200, a light absorbing layer 300, a buffer layer 400, a high resistance buffer layer 500, and a window layer 600.

The support substrate 100 has a plate shape and supports the back electrode layer 200, the light absorbing layer 300, the buffer layer 400, the high resistance buffer layer 500, and the window layer 600.

The support substrate 100 may be an insulator. The support substrate 100 may be a glass substrate, a plastic substrate, or a metal substrate. In more detail, the support substrate 100 may be a soda lime glass substrate. The supporting substrate 100 may be transparent. The support substrate 100 may be rigid or flexible.

The back electrode layer 200 is disposed on the support substrate 100. The back electrode layer 200 is a conductive layer. Examples of the material used for the back electrode layer 200 include a metal such as molybdenum (Mo).

In addition, the back electrode layer 200 may include two or more layers. In this case, each of the layers may be formed of the same metal, or may be formed of different metals.

The light absorbing layer 300 is disposed on the back electrode layer 200. The light absorbing layer 300 includes a group I-III-VI compound. For example, the light absorbing layer 300 is copper-indium-gallium-selenide-based (Cu (In, Ga) Se _2; CIGS-based) crystal structure, a copper-indium-selenide-based or copper-gallium-selenide Crystal structure.

The energy band gap of the light absorption layer 300 may be about 1 eV to 1.8 eV.

The buffer layer 400 is disposed on the light absorbing layer 300. The buffer layer 400 is in direct contact with the light absorbing layer 300.

The buffer layer 400 includes a zinc compound. The buffer layer 400 may be formed of the zinc compound.

The zinc compound is represented by the formula Zn _X A _Y , where A is selected from the group consisting of sulfur, selenium and telenium, X is greater than 0 and less than 2, and Y is greater than 0 and less than 2.

That is, the buffer layer 400 may include zinc sulfite, zinc selenide, or zinc tellurium.

In more detail, the buffer layer 400 may be formed of zinc sulfite, zinc selenide, or zinc tellurium.

For example, the buffer layer 400 may include ZnS, ZnSe, or ZnTe. In addition, the buffer layer 400 may be made of ZnS, ZnSe, or ZnTe.

In addition, X may be about 0.9 to 1.1 and Y may be about 0.9 to 1.1.

The buffer layer 400 includes silver or aluminum. In more detail, the buffer layer 400 may include silver or aluminum as a dopant.

That is, the buffer layer 400 may be made of the zinc compound, and silver or aluminum may be doped into the zinc compound.

Silver may be doped at a concentration of about 1 wt% to 10 wt%. In addition, aluminum may be doped at a concentration of 1 wt% to 10 wt%.

In addition, silver and aluminum can be doped into the zinc compound at the same time.

The buffer layer 400 may have a thickness of about 50 nm to about 150 nm. In addition, the bandgap energy of the buffer layer 400 may be about 2 eV to about 2.5 eV.

The high resistance buffer layer 500 and the high resistance buffer layer 500 are disposed on the buffer layer 400. The high resistance buffer layer 500 includes zinc oxide (i-ZnO) that is not doped with impurities. The energy bandgap of the high resistance buffer layer 500 is about 3.1 eV to 3.3 eV.

The window layer 600 is disposed on the high resistance buffer layer 500. The window layer 600 is transparent and is a conductive layer. Examples of the material used as the window layer 600 include aluminum doped ZnO (AZO).

The buffer layer contains the zinc compound instead of cadmium sulfide. That is, the solar cell according to the embodiment can form a buffer layer without using cadmium.

Therefore, the solar cell according to the embodiment does not contain heavy metals such as cadmium or the like and is very small.

Therefore, the solar cell according to the embodiment does not damage the human body and prevents contamination by heavy metals.

In addition, the buffer layer may be easily doped with silver or aluminum.

Therefore, the solar cell according to the embodiment can easily adjust the bandgap energy of the buffer layer by silver or aluminum, and can improve the overall photoelectric efficiency.

2 to 4 are cross-sectional views illustrating a process for manufacturing a solar cell according to an embodiment. This manufacturing method will be described with reference to the solar cell described above. In the description of the present manufacturing method, the foregoing description of the solar cell may be essentially combined.

Referring to FIG. 2, a metal such as molybdenum is deposited on the support substrate 100 by a sputtering process, and a back electrode layer 200 is formed. The back electrode layer 200 may be formed by two processes having different process conditions.

An additional layer such as a diffusion barrier may be interposed between the support substrate 100 and the back electrode layer 200.

Referring to FIG. 3, the light absorbing layer 300 and the buffer layer 400 are sequentially formed on the back electrode layer 200.

The light absorbing layer 300 may be formed by a sputtering process or an evaporation method.

For example, copper, indium, gallium, selenide-based (Cu (In, Ga) Se ₂ ; CIGS-based) while evaporating copper, indium, gallium, and selenium simultaneously or separately to form the light absorbing layer 300. The method of forming the light absorbing layer 300 and the method of forming the metal precursor film by the selenization process are widely used.

When the metal precursor film is formed and selenization is subdivided, a metal precursor film is formed on the back electrode 200 by a sputtering process using a copper target, an indium target, and a gallium target.

Subsequently, the metal precursor film is formed of a copper-indium-gallium-selenide-based (Cu (In, Ga) Se ₂ ; CIGS-based) light absorbing layer by a selenization process.

Alternatively, the copper target, the indium target, the sputtering process using the gallium target, and the selenization process may be performed simultaneously.

Alternatively, the CIS-based or CIG-based optical absorption layer 300 can be formed by using only a copper target and an indium target, or by a sputtering process and a selenization process using a copper target and a gallium target.

Thereafter, a zinc compound is deposited on the light absorbing layer 300 to form the buffer layer 400.

The buffer layer 400 may be formed by a chemical bath deposit (CBD) or spray method.

For example, the buffer layer 400 may be formed by a CBD process. In order to form the buffer layer 400, first, an aqueous solution containing zinc sulfate, tellurium and ammonia is prepared.

The aqueous solution may comprise about 1 mM to about 5 mM zinc sulfate, about 10 mM to about 50 mM tellurium, and about 1 mM to about 10 mM ammonia.

Thereafter, the light absorbing layer 300 is exposed to the aqueous solution. That is, the light absorbing layer 300 is in direct contact with the aqueous solution, and by the chemical reaction, the buffer layer 400 is formed on the light absorbing layer 300. In this case, the reaction temperature may be about 60 ℃ to about 80 ℃. In addition, the reaction time may be from about 10 minutes to about 15 minutes.

In addition, the aqueous solution may include a compound of silver and / or aluminum, and in the CBD process, silver and / or aluminum may be doped into the buffer layer 400.

Alternatively, the buffer layer 400 may be formed by a spray method.

For example, the zinc compound particles are dispersed in an alcohol solvent, and the solvent in which the zinc compound is dispersed is sprayed onto the light absorbing layer 300. In this case, the size of the particles of the zinc compound may be about 5nm to about 100nm. In addition, a heat treatment process may also be performed in the process of spraying the solvent.

The solvent spraying process may be performed at a temperature of about 100 ° C. to about 150 ° C., and may be performed for about 5 to 15 minutes.

Silver and / or aluminum may be dispersed in the solvent. Accordingly, silver and / or aluminum may be doped into the buffer layer 400.

Referring to FIG. 4, zinc oxide is deposited on the buffer layer 400 by a sputtering process, and the high resistance buffer layer 500 is formed.

Thereafter, the window layer 600 is formed on the high resistance buffer layer 500. In order to form the window layer 600, a transparent conductive material is stacked on the high resistance buffer layer 500. Examples of the transparent conductive material include aluminum doped zinc oxide and the like.

The method of manufacturing a solar cell according to the embodiment may provide a buffer layer 400 including the zinc compound, and thus provide a solar cell that does not include heavy metal and has improved efficiency.

Experimental Example

Molybdenum was deposited on a soda-lime glass substrate to form a back electrode layer of about 1000 nm. Thereafter, copper, indium, gallium, and selenium were deposited on the back electrode layer by a co-evaporation method to form a light absorbing layer of about 1800 nm. The light absorbing layer is then immersed in an aqueous solution containing about 3 mM ZnSO ₄ , about 30 mM Te, about 0.5 mM AgSO ₄ and about 5 mM NH ₄ OH for about 12 minutes. The temperature of the aqueous solution was about 70 ° C. As a result, a buffer layer # 1 having a thickness of about 75 nm was formed on the light absorbing layer. Thereafter, i-ZnO was deposited on the buffer layer at about 75 nm to form a high resistance buffer layer, and aluminum doped ZnO (AZO) was deposited on the high resistance buffer layer at a thickness of about 800 nm to form a window layer. It was. The bandgap energy of the buffer layer # was about 2.2 eV.

Comparative example

The remaining layers were the same as the experimental example, and the buffer layer # 2 was formed by CBD with a thickness of about 75 nm using CdS.

The solar cell of the experimental example had about 1% more output than the solar cell of the comparative example.

Although the above description has been made based on the embodiments, these are merely examples and are not intended to limit the present invention. Those skilled in the art to which the present invention pertains may not have been exemplified above without departing from the essential characteristics of the present embodiments. It will be appreciated that many variations and applications are possible. For example, each component specifically shown in the embodiment can be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

1 is a cross-sectional view showing a cross section of a solar cell according to an embodiment.

2 to 4 are cross-sectional views illustrating a process for manufacturing a solar cell according to an embodiment.

Claims (7)

Board; A light absorbing layer disposed on the substrate; A buffer layer disposed on the light absorbing layer, the buffer layer including a zinc compound represented by the following formula; And A solar cell comprising a window layer disposed on the buffer layer. Chemical formula Zn _X A _Y Where A is telenium, X is greater than 0 and less than 2, and Y is greater than 0 and less than 2. The solar cell of claim 1, further comprising a high resistance buffer layer interposed between the buffer layer and the window layer and comprising zinc oxide. The solar cell of claim 1, wherein the buffer layer comprises silver or aluminum. The solar cell of claim 1, wherein the buffer layer has a bandgap energy of about 2 eV to about 2.5 eV. Forming an electrode layer on the substrate; Forming a light absorbing layer on the electrode layer; Forming a buffer layer on the light absorbing layer, wherein the buffer layer comprises a zinc compound represented by the following formula; And The method of manufacturing a solar cell comprising the step of forming a window layer on the buffer layer. Chemical formula Zn _X A _Y Where A is telenium, X is greater than 0 and less than 2, and Y is greater than 0 and less than 2. The method of claim 5, wherein the forming of the buffer layer Forming a solution comprising zinc sulfate and A; And The method of manufacturing a solar cell comprising the step of exposing the light absorbing layer to the solution. The method of claim 5, wherein the forming of the buffer layer Dispersing the zinc compound in a solvent; And Spraying a solvent in which the zinc compound is dispersed in the light absorbing layer.

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