KR100625082B1 - Fabrication of InxOOH,Sy Buffer Layer by Chemical Bath Deposition for CuIn,GaSe2 or CuIn,GaS,Se2 Thin Film Solar Cells and Solar Cells manufactured by thereof - Google Patents

Abstract

Indium oxyhydrooxide sulfide buffer layer for Cu (In, Ga) Se ₂ (hereinafter “CIGS”) or Cu (In, Ga) (S, Se) ₂ (hereinafter “CIGSS”) thin film solar cell using solution growth method The present invention relates to a manufacturing method and a solar cell manufactured therefrom, and an object thereof is to provide a method for manufacturing a new buffer layer material, an indium oxyhydrooxide sulfide thin film, having a thickness of several tens of nanometers by a solution growth method which is a low cost process, and a solar cell thereof. . The configuration of the present invention is a method of manufacturing a buffer layer applied to a thin film solar cell using a CIGS or CIGSS compound semiconductor as the light absorption layer, the indium oxyhydrooxide sulfide thin film to prepare a buffer layer by a solution growth method without the need for further heat treatment, wherein the solution The growth method uses an indium chloride as the source of indium and thioacetamide as the source of sulfur and an aqueous solution of acetic acid added thereto as a starting solution.The pH of the solution is 2.2 to 3 and the temperature is 60. The reaction time in a solution of -80 ° C and the solution is between 5 and 30 minutes, and a method for producing the solar cell.

Solution growth method, solar cell, buffer layer, indium oxyhydrooxide sulfide, Cu (Inn), S, Se

Description

Method for preparing indium oxyhydrooxide sulfide buffer layer for Cu (Inn), Ce2 or Cu (2) thin film solar cell using solution growth method and solar cell manufactured therefrom {Fabrication of Inx (OOH, S) y Buffer Layer by Chemical Bath Deposition for Cu (In, Ga) Se2 or Cu (In, Ga) (S, Se) 2 Thin Film Solar Cells and Solar Cells manufactured by             

1 is a spectrum using X-ray photoelectron spectroscopy (XPS) of an indium oxyhydrooxide sulfide thin film deposited on Corning glass using the solution growth method of the present invention,

FIG. 2 is an X-ray diffraction (XRD) pattern of the indium oxyhydrooxide sulfide thin film of FIG. 1 deposited on a substrate by the present invention.

3 is an X-ray diffraction (X-ray Diffraction; XRD) pattern of the indium oxide sulfide In (O, S) thin film obtained by heat-treating the indium oxyhydrooxide sulfide thin film deposited by the present invention for 4 hours at 500 ℃,

4 is a scanning micrograph of the cross section and surface of the indium oxyhydrooxide sulfide thin film of FIG. 1 deposited on a Corning glass substrate;

5 is a surface scanning micrograph of an indium oxyhydrooxide sulfide thin film deposited on a CIGS thin film,

FIG. 6 is a light transmission comparison diagram of the indium oxyhydrooxide sulfide and the conventional cadmium sulfide thin film of FIG. 1 deposited on a Corning glass substrate. FIG.

7 is a process for manufacturing a CIGS thin film solar cell using the indium oxyhydrooxide sulfide thin film of FIG.

8 is a current density-voltage curve of an optical state of a CIGS solar cell using the indium oxyhydrooxide sulfide thin film developed in the present invention as a buffer layer.

<Description of the symbols for the main parts of the drawings>

(1): soda lime glass

(2): molybdenum deposited by sputtering method

(3): Cu (In, Ga) Se ₂ thin film deposited by vacuum evaporation method or Cu (In, Ga) (S, Se) thin film deposited by sputtering

(4) Indium oxyhydrooxide sulfide thin film deposited by solution growth method

(5) Zinc oxide deposited by sputtering or metal organic chemical vapor deposition

(6): aluminum front electrode using vacuum evaporation

The present invention relates to a method for preparing an indium oxyhydrooxide sulfide buffer layer for Cu (In, Ga) Se ₂ or Cu (In, Ga) (S, Se) ₂ thin film solar cell using a solution growth method and a solar cell prepared therefrom. In detail, a thin film solar cell using Cu (In, Ga) Se ₂ (hereinafter referred to as “CIGS”) or Cu (In, Ga) (S, Se) ₂ (hereinafter referred to as “CIGSS”) compound semiconductor as a light absorption layer The present invention relates to a method for manufacturing a buffer layer applied to a CGS (or 'CIGSS') solar cell. Until now, a cadmium sulfide thin film has been mainly used as a buffer layer. _{The present} invention relates to a method for producing a _x (OOH, S) _y thin film using chemical bath deposition, and a solar cell having such a thin layer.

Prior art for the indium series instead of the conventional cadmium used as the buffer layer of the CIGS thin film solar cell is as follows.

The first is the technology of manufacturing indium oxysulfide (In ₂ S _3-x O _x ) by vacuum evaporation method (French patent, application number 9810603, application date 1998.08.21, notification number 2782574, notification date 2002.02.25), x value Reported the best solar cell performance at 0.25, ranging from 0.15 to 0.35.

However, the technique is a vacuum evaporation method that requires expensive vacuum equipment, and after the deposition requires a heat treatment for about 25-30 minutes in an 342 ℃ oxygen atmosphere, there is a disadvantage in terms of manufacturing cost.

Another indium buffer layer is an indium sulfide manufacturing technique (Spiering, Thin Solid Films, 2003, Vol. 431-432, 359) by Atomic Layer Chemical Vapor Deposition. Indium acetylacetonate and hydrogen sulfide (H ₂ S) were used as precursors for atomic layer chemical vapor deposition, and reported excellent solar cell performances approaching 15% conversion efficiency.

However, the atomic layer chemical vapor deposition method can control the material at the atomic level to obtain a very good film quality, but it takes a long time to obtain a thin film of the same thickness, and the equipment itself is expensive, which is also a low cost CIGS thin film solar The disadvantage is that it is not suitable for battery technology.

In addition, the solution growth method, which is a low-cost process, is a technique for preparing hydroxide sulfide In _x (OH, S) _y using indium (III) chloride and thiacetamide as a source of indium and sulfur (Hariskos, Solar Energy Materials and Solar Cells, 1996 , Vol. 41/42, 345). The result of applying this buffer layer thin film to CIGS solar cell reported more than 15% of solar cell conversion efficiency.

However, when the indium hydroxide sulfide thin film is applied as a buffer layer, there is a disadvantage in that a subsequent heat treatment to reduce the efficiency is required since the light soaking effect is generally lowered when exposed to initial light.

An object of the present invention for solving the above problems is to provide a method for manufacturing a new buffer layer material indium oxyhydrooxide sulfide thin film to a thickness of several tens of nanometers by a solution growth method which is a low-cost process.

In addition, this method can be applied to CIGS (or 'CIGSS') thin film solar cells to increase the light transmittance in the short wavelength region, to reduce the series resistance of the solar cells, and to improve the interfacial properties between the buffer layer and other thin films. It is to provide an efficient solar cell.

The present invention to achieve the object as described above and to solve the conventional drawbacks can be used as a buffer layer instead of the conventional cadmium sulfide in a thin film solar cell using a CIGS (or 'CIGSS') compound semiconductor as the light absorption layer A new material, indium oxyhydrooxide sulfide thin film is prepared by the solution growth method.

In the solution growth method, an aqueous solution is prepared by using indium chloride (InCl ₃ ) as a source of indium and thiacetamide (CH ₃ CSNH ₂ ) as a source of sulfur, and then put into an reaction vessel. The temperature in the reaction vessel and the hydrogen ion of the solution The indium oxyhydrooxide sulfide thin film is grown by adjusting the concentration (pH) and the retention time in solution.

In order to manufacture a CIGS (or 'CIGSS') thin film solar cell, an indium oxyhydrooxide sulfide thin film is generally grown on a substrate having a molybdenum (Mo) / CIGS (or 'CIGSS') structure and sputtered thereon. Zinc oxide (ZnO) to be used as a transparent conductive film is deposited, and an aluminum thin film is sequentially stacked by a vacuum evaporation method as a front electrode.

The solution to be used in the solution growth method is made of indium chloride and thiacetamide by adding acetic acid in the reaction vessel, where the proper pH is adjusted to 2.2-3.0.

The reaction vessel uses a thermostatic bath to raise the temperature of the solution in the reaction vessel to 68 ° C. for 13 minutes and then grows (deposits) the thin film while maintaining the substrate in the solution for 5-30 minutes.

At this time, when the pH of the solution is lower than 2.2, the thin film shows a very rough surface because the formation of indium oxyhydrooxide and indium sulfide is delayed and the size of the deposited particles is also increased. On the contrary, when the hydrogen ion concentration (pH) is higher than 3.0, the reaction rate is so fast that the reproducibility of thin film production is poor.

The temperature of the solution is also a very important factor in controlling the reaction rate. The surface properties are also very dependent on the deposition time. If the deposition time is longer than necessary (greater than 30 minutes), the thickness becomes thick as well as the porous network structure, which is undesirable because it increases the recombination current density of the solar cell. In addition, since the GIGS (or 'GIGSS') layer, which is less than 5 minutes, cannot be completely covered with an indium oxyhydrooxide sulfide thin film, the photovoltaic characteristics are adversely affected by the increase in recombination current density after solar cell manufacturing. Therefore, control of deposition time is essential for obtaining a thin, uniform thickness of clean indium oxyhydrooxide sulfide thin film of several tens of nanometers.

Hereinafter, the configuration and the operation of the embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an aqueous solution using indium (III) chloride (InCl ₃ ), which is a source of indium ions, and thiacetamide (CH ₃ CSNH ₂ ), which is a source of sulfur, using a solution growth method. Spectra using X-ray photoelectron spectroscopy (XPS) of indium oxyhydrooxide sulfide thin films deposited on Corning glass. This analysis shows the chemical composition of the indium oxyhydrooxide sulfide thin film, and it can be seen that there is no indium hydrooxide In (OH) ₃ in the thin film.

In more detail, the chemically bonded structure of the thin film deposited by the above method for 20 minutes was observed by X-ray photoelectron spectroscopy, and peaks of indium, oxygen, and sulfur were observed in the deposited thin film. In 3d _5/2 (a) of indium, O 1s (a) of oxygen, and S 2p (d) of sulfur are located at 445.2 eV, 531.7 eV, and 161.8 eV, respectively, which represent indium oxide (In ₂ O ₃₎ in the thin film. ), Indium hydrooxide In (OH) ₃ , or indium sulfide (In ₂ S ₃ ) is possible. However, the presence of In ₂ S ₃ was confirmed in In MNN (B), which is the Auger peak of indium, but the presence of indium oxide and indium hydroxide was not confirmed. It was confirmed that the thin film was composed of an indium compound bonded to oxygen in addition to indium sulfide.

FIG. 2 is an X-ray diffraction (XRD) pattern of the indium oxyhydrooxide sulfide thin film of FIG. 1 deposited on a substrate. FIG. It can be seen that the thin film consists of indium oxyhydrooxide and indium sulfide. In the figure, (a) is a Corning glass substrate, and (b) is a CIGS substrate.

3 is an indium oxide sulfide In (O, S) thin film obtained by heat-treating the deposited indium oxyhydrooxide sulfide thin film at 500 ° C. for 4 hours.

4 is a scanning micrograph of the cross section and surface of the indium oxyhydrooxide sulfide thin film of FIG. 1 deposited on a Corning glass substrate. The thickness and surface structure change with deposition time is shown. In the figure, (a) and (b) are deposited for 15 minutes, (c) and (d) are deposited for 20 minutes, and (e) and (b) are deposited for 30 minutes.

It shows the surface structure of the indium oxyhydrooxide sulfide thin film according to the deposition time. When the deposition time is 20 minutes or less, the thin film shows the structure of particles having a size of 10-20 nm, and when the deposition time is 30 minutes or more, the thin film is Sponge-shaped mesh structure is shown.

5 is a surface scanning micrograph of an indium oxyhydrooxide sulfide thin film deposited on a CIGS thin film. The change in surface structure with time of deposition is shown. In the figure, (a) is deposited for 20 minutes, and (b) is deposited for 25 minutes.

FIG. 6 compares the light transmittance of the indium oxyhydrooxide sulfide of FIG. 1 deposited on a Corning glass substrate with a conventional cadmium sulfide thin film. Although the indium oxyhydrooxide sulfide thin film in the short wavelength region is thicker than the cadmium sulfide thin film, it exhibits excellent light transmittance especially in the short wavelength region.

FIG. 7 illustrates a process of manufacturing a CIGS thin film solar cell using the indium oxyhydrooxide sulfide thin film of FIG. 1.

(end). Depositing molybdenum (Mo) on soda-lime glass using a sputtering method; (I). CIGS or CIGSS deposition using vacuum evaporation or sputtering; (All). Indium oxyhydrooxide sulfide deposition using a solution growth method; (la). Zinc oxide deposition using sputtering or metal organic chemical vapor deposition; (hemp). Aluminum front electrode manufacturing and electrode wiring step using vacuum evaporation method.

Reference numeral 1 denotes soda-lime glass, 2 molybdenum deposited by sputtering method, 3 GIGS thin film deposited by vacuum evaporation method or GIGSS thin film deposited by sputtering method, 4 is indium oxyhydrooxide deposited by solution growth method. The sulfide thin film, 5 is zinc oxide deposited by sputtering or metal organic chemical vapor deposition, and 6 is an aluminum front electrode using vacuum evaporation.

8 is a current density-voltage curve of an optical state of a CIGS solar cell using the indium oxyhydrooxide sulfide thin film developed in the present invention as a buffer layer. For CIGS solar cells, efficiency 10.0%, short circuit current 32.1 mA / cm ² , open voltage 560 mV, and fidelity 55% were obtained. For CIGSS solar cells, efficiency 12.55%, short circuit current 33.17 mA / cm2, open voltage 574. mV, and fidelity 65.89%.

The following is a preferred embodiment of the present invention.

<Example 1>

0.03 M of indium chloride and 0.1 M of thiacetamide solution were mixed in the reaction vessel, and acetic acid was added thereto to adjust the hydrogen ion concentration (pH) of the solution to about 2.0. The reaction vessel was placed in a thermostat and the temperature of the solution was raised using a bath. Glass or molybdenum / CIGS substrate to be used as a substrate was added when the solution temperature reached 24 ℃, the temperature was raised for 13 minutes to reach 68 ℃ and then maintained for 15, 20 and 30 minutes to deposit a thin film. When deposited for 15 minutes, an indium oxyhydrooxide sulfide thin film having a thickness of 32.2 nm was obtained. When the deposition time was 20 minutes, 43 nm, which is a preferable thickness, was obtained as the buffer layer of the solar cell. As the deposition time increases, the thickness increases, and when the film is deposited for 30 minutes, a thin film having a thickness of 146 nm can be obtained.

<Example 2>

The deposition process was repeated in the same manner as in Example 1 to obtain a thick film. 2 shows that indium oxyhydrooxide and indium sulfide coexist in the thin film as a result of X-ray diffraction analysis.

<Example 3>

FIG. 3 is an X-ray diffraction analysis result after depositing an indium oxyhydrooxide sulfide thin film on a Corning glass substrate in the same manner as Example 1 and performing heat treatment for 4 hours at 500 ° C. in a nitrogen atmosphere. Indium oxide (In ₂ O ₃ JCPDS 65-3170) is formed in addition to the indium sulfide known in Example 2. This is a phase in which the indium oxyhydrooxide phase is dehydrated, which is another evidence of the presence of indium oxyhydrooxide in the thin film before heat treatment.

<Example 4>

FIG. 8 is a method of manufacturing a solar cell by growing an indium oxyhydrooxide sulfide thin film having a thickness of 40 nm on a molybdenum / CIGS substrate in the same manner as in Example 1, and then stacking a transparent electrode and a front electrode. The current-voltage curve is measured.

The CIGS light absorbing layer thin film was prepared by co-vacuum evaporation on a molybdenum-coated soda-lime glass substrate.

The i-type and n-type zinc oxide thin films were prepared by the sputtering method as the transparent electrode, and the aluminum thin film was prepared by the electron beam vacuum evaporation method for the front electrode to complete the solar cell.

As a result of measuring light distribution and intensity of AM 1.5, a solar cell conversion efficiency of 10% was obtained.

In the same way, conversion efficiency of 12.55% was obtained using CIGSS as light absorption layer instead of CIGS.

The present invention is not limited to the above-described specific preferred embodiments, and various modifications can be made by any person having ordinary skill in the art without departing from the gist of the present invention claimed in the claims. Of course, such changes will fall within the scope of the claims.

As described above, the present invention provides an indium oxyhydrooxide sulfide thin film which can be used as a new buffer layer instead of the existing cadmium sulfide which may cause cadmium toxicity problem in a thin film solar cell using a CIGS (or 'CIGSS') compound semiconductor as a light absorbing layer. It can be manufactured by the solution growth method, and the use of this material as a buffer layer can improve the light transmittance in the short wavelength region, lower the series resistance of the solar cell, and improve the interfacial properties between the buffer layer and other thin films, which is inexpensive. An advantage is that an efficient solar cell can be manufactured.

In addition, the present invention has the advantage that the indium oxyhydrooxide sulfide thin film manufactured by the solution growth method, which is a process capable of mass production at low cost, does not need high temperature heat treatment later.

In addition, the present invention is a useful invention that has the advantage of controlling the composition of the solution, hydrogen ion concentration (pH), the reaction time to the thickness of the nanometer level, and the growth of very high uniformity thin film is possible industrially It is an invention that the use is expected greatly.

Claims (2)

In the manufacturing method of the buffer layer applied to the thin film solar cell which uses CIGS or CIGSS compound semiconductor as a light absorption layer, The indium oxyhydrooxide sulfide thin film is prepared by a solution growth method without the need for further heat treatment, and the solution growth method is an aqueous solution in which indium chloride is used as the source of indium and thiacetamide is used as the source of sulfur, and acetic acid is added thereto. Using a solution growth method characterized in that the starting solution, the hydrogen ion concentration (pH) of the solution is prepared so that the 2.2-3 temperature is 60 ~ 80 ℃, the reaction time in the solution is 5 ~ 30 minutes Method for preparing an indium oxyhydrooxide sulfide buffer layer for Cu (In, Ga) Se ₂ or Cu (In, Ga) (S, Se) ₂ thin film solar cell. Cu (In, Ga) Se ₂ or Cu (In, Ga) (S, Se) ₂ thin film using a solution growth method comprising an indium oxyhydrooxide sulfide thin film buffer layer prepared by the method of claim 1 A solar cell manufactured by the method for producing an indium oxyhydrooxide sulfide buffer layer for a solar cell.

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