CN100466298C - Manufacturing method of solar cell absorber layer - Google Patents

Abstract

The present invention relates to a method of manufacturing CuInSe ₂ and CuIn _1-x Ga _x Se ₂ thin films for use as absorber layers in solar cells, said thin films having a composition close to the chemical equivalence ratio. The method for manufacturing a thin film for a solar cell provided by the invention comprises: using [Me ₂ In-(μSeMe)] ₂ precursor to form an InSe thin film on a substrate by metal organic chemical vapor deposition; using (hfac)Cu(DMB) Precursor, Cu ₂ Se film was formed on InSe film by metal organic chemical vapor deposition; and CuInSe was formed on Cu ₂ Se film by metal organic chemical vapor deposition using [Me ₂ In-(μSeMe)] ₂ precursor ₂ compound films. The method also includes using [Me ₂ Ga-(μSeMe)] ₂ precursor to form a CuIn _1-x Ga _x Se ₂ film on the CuInSe ₂ compound film by metal organic chemical vapor deposition.

Description

Manufacturing method of solar cell absorber layer

technical field

The present invention relates to a method of manufacturing an absorber layer of a solar cell, and more particularly to a _method of using MOCVD to manufacture _CuInSe2 and _{CuIn1-xGaxSe2 thin} films, the composition of which is close to the stoichiometric ratio ( chemical equivalence ratio).

Background technique

A triple thin film of CuInSe ₂ (hereinafter referred to as “CIS”) or CuIn _1-x Ga _x Se ₂ (hereinafter referred to as “CIGS”) is a semiconductor compound that has been actively studied recently.

Unlike conventional solar cells using silicon, the CIS-based thin-film solar cells can be made thinner than 10 micrometers in thickness and have stable performance even after long-term use. In addition, it has been confirmed through experiments that the energy conversion rate of CIS-based thin-film solar cells is as high as 19%, which is superior to other solar cells, so it is very promising to commercialize it as a low-cost and high-efficiency solar cell that can replace silicon.

In this regard, various methods of producing CIS thin films have been reported recently. For example, US4523051 discloses a method of simultaneously vapor-depositing elemental metals under a vacuum atmosphere. However, this method uses an expensive effusion cell, and thus is not economical for mass production and realizing a large area. US 4,798,660 discloses another method of heating and selenizing a Cu-In precursor under a selenium-containing gas atmosphere such as _H2Se . However, _H2Se gas is highly toxic to the human body and thus dangerous in the mass production of CIS thin films. Other methods such as electrodeposition and molecular beam epitaxy have also been proposed, but these methods are expensive or only suitable for laboratory scale, so they are not suitable for large-scale production of CIS thin films.

Therefore, in order to achieve mass production of high-quality CIS thin films, it is most preferable to use Metal Organic Chemical Vapor Deposition (Metal Organic Chemical Vapor Deposition, hereinafter referred to as "MOCVD"), which is widely used in conventional semiconductor processes.

However, MOCVD is a generalized technique capable of producing high-quality thin films at low cost in the semiconductor industry, but the production of CIS solar cells using conventional MOCVD techniques encounters problems related to high production costs and complex processes, making mass production difficult High quality film.

For the formation of CIS or CIGS thin films, a conventional method involves sputtering molybdenum to be vapor-deposited onto a glass substrate, which is then used as a substrate for thin film formation. However, glass substrates do not have flexibility, so there is a problem that glass substrates cannot be used where free deformation is required.

Contents of the invention

Therefore, the present invention has been accomplished based on the above problems, and an object of the present invention is to provide a method of manufacturing CIS and CIGS thin films having compositions close to stoichiometric ratios using MOCVD.

Another object of the present invention is to provide a method for manufacturing CIS or CIGS thin films for solar cells by using MOCVD, which has a simple preparation process and can be mass-produced at low cost.

Yet another object of the present invention is to provide a method for manufacturing CIS or CIGS thin films for solar cells, which is less harmful to human body and more environment-friendly.

Another object of the present invention is to provide a method for manufacturing a freely deformable or bendable CIS or CIGS thin film for solar cells.

Description of drawings

The above and other objects, features and other advantages of the present invention will be more clearly understood through the following detailed description in conjunction with the accompanying drawings. in:

Fig. 1 briefly describes the process flow of manufacturing CuInSe _thin film according to the first embodiment of the present invention;

Fig. 2 is a graph showing the XRD (X-ray diffraction) results of the InSe thin film produced according to the present invention;

Fig. 3 is a graph showing the XRD (X-ray diffraction) results of Cu ₂ Se thin films produced according to the present invention;

Fig. 4 is a graph showing the XRD (X-ray diffraction) results of the CuInSe _thin film generated according to the present invention;

Fig. 5 briefly describes the process flow of manufacturing CuIn _1-x Ga _x Se ₂ thin film according to the second embodiment of the present invention;

Fig. 6 is a graph showing the XRD (X-ray diffraction) results of CuIn _1-x Ga _x Se ₂ films produced according to the present invention;

Fig. 7 is a _graph showing the variation of lattice constants 2a and c with the ratio of [Ga]/[In+Ga] in CuIn1 _{- xGaxSe2} thin films produced according to the present invention;

Fig. 8 is a chart showing the composition ratio of the _CuInSe2 film formed according to the present invention;

Fig. 9 is a graph showing the composition ratio of the CuIn _1-x Ga _x Se ₂ film formed according to the present invention;

10 to 14 are SEM images of CuIn _1-x Ga _x Se ₂ thin film samples AE formed according to the present invention.

Detailed ways

The manufacturing method of the CIS or CIGS thin film according to the preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

FIG. 1 briefly describes the process flow of manufacturing a CIS thin film according to the first embodiment of the present invention.

As shown in FIG. 1 , an InSe thin film is formed on a substrate made of molybdenum (Mo) material by MOCVD using a single precursor [Me ₂ In(μSeMe)] ₂ containing In and Se (step S101 ). Me represents a methyl group, and μ represents that Se and In are connected by double bonds. A thin and flexible substrate made of a molybdenum material can be used as the substrate instead of a conventional glass substrate, and thus various shapes of solar cells can be realized.

Next, a Cu ₂ Se thin film is formed on the InSe thin film formed in Step S101 by MOCVD using a monovalent copper precursor (hfac)Cu(DMB) (Step S102 ). Hfac and DMB are abbreviations for hexafluoroacetylacetonate and 3,3-dimethyl-1-butene, respectively.

Then, a CuInSe ₂ thin film is formed on the Cu ₂ Se thin film formed in step S102 by MOCVD using a single precursor [Me ₂ In(μSeMe)] ₂ containing In and Se (step S103 ). The precursor [Me ₂ In(μSeMe)] ₂ used to form the CuInSe ₂ thin film is the same as that used in step S101.

In the present invention, the device for forming the thin film is a low-pressure MOCVD device. The low-pressure MOCVD equipment used in the present invention is equipped with a plurality of bubblers (bubblers), and the bubblers contain precursors such as (hfac)Cu(DMB), [Me ₂ In-(μSeMe)] ₂ and [Me ₂ Ga -(μSeMe)] ₂ . Therefore, CIGS thin films can be prepared in a single process using the bubblers containing the respective precursors sequentially.

FIG. 2 shows the XRD results of the InSe thin film formed in step S101. Figure 2 shows that the structure of the β-InSe structure is very good and the formed InSe film shows a good yield.

FIG. 3 shows the XRD results of the Cu ₂ Se thin film formed in step S102. It can be seen that the original InSe film has become a Cu ₂ Se film. X-ray fluorescence spectroscopy (XRF) analysis confirmed that no In was detected and the film was completely made of Cu ₂ Se. That is, when copper was grown on an InSe thin film by MOCVD using a monovalent copper precursor (hfac)Cu(DMB), the original In disappeared and was replaced by Cu, thus indicating that InSe was transformed into Cu ₂ Se.

FIG. 4 shows the XRD results of the CuInSe ₂ thin film formed in step S103. It can be seen that the XRD pattern of the CuInSe ₂ film produced is consistent with the known CuInSe ₂ single crystal. The resulting films exhibit a single phase with a tetragonal lattice.

Fig. 5 briefly describes the process flow of manufacturing CuIn _1-x Ga _x Se ₂ thin film according to the second embodiment of the present invention.

As shown in FIG. 5, steps S201-S203 are the same as the above-mentioned CIS film preparation process. A CuIn 1-x Ga x Se ₂ film is formed by MOCVD on the CuInSe ₂ film formed in Step S203 using a precursor [Me ₂ Ga(µSeMe)] ₂ containing Ga _{and Se} (Step S204 ). [Me ₂ Ga(μSeMe)] ₂ is a precursor substance, wherein In in [Me ₂ In(μSeMe)] ₂ is replaced by Ga.

In order to analyze the physical properties related to the composition ratio of In and Ga of the CIGS thin film generated, adjust the composition ratio of In and Ga by changing the time of vapor deposition in step 204, prepare 5 samples with different composition ratios (A, B, C, D and E). In the CuIn _1-x Ga _x Se ₂ thin films, the x values measured by X-ray fluorescence spectroscopy, that is, the composition ratios of [Ga]/[In+Ga] are 0, 0.062, 0.19, 0.34 and 0.96, respectively.

Fig. 6 shows XRD results of CuIn _1-x Ga _x Se ₂ thin films A, B, C, D and E produced in the second embodiment of the present invention. According to the composition ratio of [Ga]/[In+Ga], the position of the peak is converted into an increasing angle (2θ).

和

与Gryunova得到的结果一致。在得到的CuIn_1-xGa_xSe₂薄膜中，x的最高值为0.96(样品E)。在这种情况下，晶格常数

和

与Gryunova报道的晶格常数和

是一致的。Fig. 7 is a graph showing the lattice constants 2a and c as a function of the value of x, ie the ratio of [Ga]/[In+Ga]. As shown in Fig. 7, the lattice constants 2a and c decrease linearly as the value of x increases. Therefore, the rate of change of lattice constants 2a and c with the [Ga]/[In+Ga] ratio is 0.329 and 0.602, respectively, indicating a significant difference between them. Furthermore, the lattice constant of the _CuInSe2 thin film

and

Consistent with the results obtained by Gryunova. In the obtained CuIn _1-x Ga _x Se ₂ film, the highest value of x is 0.96 (sample E). In this case, the lattice constant

and

With the lattice constant reported by Gryunova and

is consistent.

8 and 9 respectively show the composition ratios of the CIS thin film formed according to the first embodiment of the present invention and the CIGS thin film formed according to the second embodiment of the present invention. The lines connecting (In+Ga) ₂ Se ₃ and Cu ₂ Se and the vertical lines defined by Groenink and Janse represent non-molecularity and non-stoichiometry, respectively. The circle at the center of the triangle is a point where the composition ratio is Cu:In:Se=1:1:2.

The dots in FIG. 8 represent a number of CuInSe ₂ samples prepared by experiments. It can be seen that the Cu:In:Se ratio of the CIS film produced according to the present invention is close to 1:1:2. In addition, the dots B, C, D, and E in Fig. 9 represent the samples with [Ga]/[In+Ga] composition ratios of 0.062, 0.19, 0.34, and 0.96, respectively, so it can be seen that even when the CIGS thin film When changing the ratio of In and Ga, Cu:(In, Ga):Se is almost kept at 1:1:2.

It can be seen from the above that the CIS thin film and the CIGS thin film prepared according to the present invention have a very close stoichiometric ratio. Therefore, high-quality thin films with expected equivalence ratios can be fabricated simply by MOCVD on a large scale without difficulty. In addition, even when the ratio of [Ga]/[In+Ga] is adjusted as needed, a thin film of Cu:In(Ga):Se close to 1:1:2 can be obtained.

10 to 14 are SEM images of CIGS thin film samples A, B, C, D and E formed according to the present invention, respectively. All samples exhibit crystal growth of stable grains, indicating that crystal growth proceeds well regardless of the [Ga]/[In+Ga] ratio composition.

Furthermore, according to the third embodiment of the present invention, by using [Me ₂ In-(μTeMe)] ₂ or [Me ₂ In-(μSMe)] ₂ instead of the [Me2Ga- (μSeMe)] ₂ , a part of Se can be replaced by Te or S, and as a result, thin film CuIn(Se,S) or CuIn(Se,Te) is obtained.

Although the present invention has been described in the preferred embodiments, the technical aspects of the present invention are not limited thereto. That is, even though the preparation methods of CuIn _1-x Ga _x Se ₂ (assuming 0≤x≤1) and CuIn(Se,S) thin films are described as thin films for solar cells, these thin films are only made of A few examples of I-III-VI ₂ compounds composed of elements from groups I, III and VI of the periodic table.

Some specific examples are described below. First, as a first step, a III-VI thin film is formed by metal-organic chemical vapor deposition using a single precursor containing group III and VI elements. Group III elements include all elements belonging to group III of the periodic table of elements, such as In, Ga or Al; group VI elements include all elements belonging to group VI of the periodic table of elements, such as Se, S or Te. The resulting III-VI films are InSe, GaSe, AlSe, InS, GaS, AlS, InTe, GaTe or AlTe.

In the second step, I2-VI thin films are formed on III-VI thin _films by metal-organic chemical vapor deposition using precursors (including monovalent or divalent precursors) containing group I metals such as Ag or Cu . Group I elements include all elements belonging to group I of the periodic table, such as Cu or Ag. Therefore, the formed I ₂ -VI film is Cu ₂ Se, Cu ₂ S, Cu ₂ Te, Ag ₂ Se, Ag ₂ S or Ag ₂ Te.

In the third step, the I-III-VI ₂ film is formed on the I ₂ -VI film by metal-organic chemical vapor deposition using a single precursor containing group III and VI elements, thus completing the solar cell according to the present invention Use film. Here, the group III and VI elements are the same as those used in the first step.

Furthermore, in the fourth step, solid solution semiconductors of I-III-VI ₂ thin films can be prepared by metal-organic chemical vapor deposition on I-III-VI ₂ thin films using a single precursor containing additional elements from groups III and VI compound. In this case, the group III and VI elements used here are different from those used in the first and third steps. Thus, the resulting films include CuIn _1-x Ga _x Se ₂ , CuIn _1-x Al _x Se ₂ , CuGa _1-x Al _x Se ₂ , AgIn _1-x Ga _x Se ₂ , AgIn _1-x Al _x Se ₂ , AgIn _1-x Ga _x Se ₂ , CuIn(Se, S) ₂ , CuGa(Se, S) ₂ , AgIn(Se, S) ₂ , AgGa(Se, S) ₂ , CuIn(Se, Te) ₂ , CuGa(Se, Te) ₂ , AgIn(Se, Te) ₂ , AgGa(Se, Te) ₂ , CuIn(S, Te) ₂ , CuGa(S, Te) ₂ , AgIn(S, Te) ₂ and AgGa( S, Te) ₂ .

Therefore, the technical aspect of the present invention should also be understood as disclosing a method for preparing I-III-VI ₂ compound and its solid solution.

The single precursors containing group III and VI elements of the present invention are not limited to the [Me ₂ (III)-(μ(VI)Me)] type precursors used in the first, second and third embodiments of the present invention precursors, it is obvious to those skilled in the art that other types of precursors not enumerated in the present invention can be used. In short, due to the similar chemical properties of elements belonging to the same group of the periodic table, similar results can be obtained even with different precursors. Likewise, the copper-containing precursor is not limited to (hfac)Cu(DMB).

Industrial Applicability

It is obvious from the above description that according to the present invention, high-quality CuIn _1-x Ga _x Se ₂ thin films for solar cells with expected equivalent ratios can be produced by simply controlling the conditions for the formation of semiconductor compounds.

Moreover, according to the present invention, low-cost mass production of CuIn _1-N Ga _x Se ₂ thin films for solar cells can be realized through a simple manufacturing process.

In addition, according to the present invention, by using a compound with relatively low toxicity as a precursor for manufacturing CuIn _1-N Ga _x Se ₂ thin films for solar cells, the production process can be made safer and more environmentally friendly.

Furthermore, the present invention uses a flexible metal as a base material, so the shape of the solar cell can be freely changed as required, thus expanding the application field.

Although the preferred embodiment of the invention has been disclosed for purposes of illustration, it will be appreciated by those skilled in the art that various changes may be made without departing from the scope and spirit of the invention as disclosed in the appended claims , Add and Replace.

Claims (10)

1. A method of manufacturing I-III-VI ₂ thin films, the method comprising: The first step: using a single precursor containing group III and group VI elements to form a III-VI compound film on the substrate by metal-organic chemical vapor deposition; Step 2: using a precursor containing a group I metal to form an I ₂ -VI compound film on the III-VI compound film by metal-organic chemical vapor deposition; and The third step: using a single precursor containing group III and VI elements to form an I-III-VI ₂ compound film on the I ₂ -VI compound film by metal-organic chemical vapor deposition. 2. The method of claim 1, further comprising a fourth step: using a single precursor containing group III and VI elements, the I-III-VI formed in the third step by metal organic chemical vapor deposition I-III-VI ₂ compound film was prepared on the ₂ compound film, wherein the group III elements used in the fourth step were different from those used in the first step and the third step. 3. The method of claim 1, further comprising a fourth step: using a single precursor containing group III and VI elements, the I-III-VI formed in the third step by metal organic chemical vapor deposition ₂ compound thin film prepared I-III-VI ₂ compound thin film, wherein the group VI element used in the fourth step is different from the element used in the first step and the third step. 4. The method according to any one of claims 1-3, wherein the precursor used in the first step and the third step is [Me ₂ In-(μSeMe)] ₂ . 5. The method according to any one of claims 1-3, wherein the precursor used in the second step is (hfac)Cu(DMB). 6. The method as claimed in claim 2, wherein the precursor used in the fourth step is [Me ₂ Ga-(μSeMe)] ₂ . 7. The method as claimed in claim 2, wherein the I-III-VI ₂ compound film formed in the fourth step is selected from CuIn _1-x Ga _x Se ₂ , CuIn _1-x Al _x Se ₂ , CuGa _{1- x} Al _x Se ₂ , AgIn _1-x Ga _x Se ₂ , AgIn _1-x Al _x Se ₂ and AgIn _1-x Ga _x Se ₂ . 8. The method as claimed in claim 3, wherein the I-III-VI ₂ compound thin film formed in the fourth step is selected from CuIn(Se,S) ₂ , CuGa(Se,S) ₂ , AgIn(Se,S) ) ₂ , AgGa(Se, S) ₂ , CuIn(Se, Te) ₂ , CuGa(Se, Te) ₂ , AgIn(Se, Te) ₂ , AgGa(Se, Te) ₂ , CuIn(S, Te) ₂ , CuGa(S, Te) ₂ , AgIn(S, Te) ₂ and AgGa(S, Te) ₂ are in the group. 9. A method of making an absorber layer for a solar cell, the method comprising: Forming InSe thin films on substrates by metal-organic chemical vapor deposition using a single precursor containing In and Se; using a Cu precursor to form a Cu ₂ Se film on the InSe film by metal organic chemical vapor deposition; and Using a single precursor containing In and Se, CuInSe ₂ compound thin films were formed on Cu ₂ Se thin films by metal-organic chemical vapor deposition. 10. The method of claim 9, further comprising the step of forming a _{CuIn1-xGaxSe2 film on} the _CuInSe2 compound film by metal organic chemical vapor deposition using a single precursor containing Ga and Se .

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