KR102042656B1 - A solar cell comprising czts thin film with uniform composition and a method of manufacturing the same - Google Patents

Abstract

The substrate is a method of manufacturing a CZTS-based thin film solar cell, comprising the steps of preparing a substrate (S1), forming a first electrode on the substrate (S2); Depositing a Cu precursor, a Sn precursor, and a Zn precursor on the first electrode to form two or more Cu precursor layers, a Sn precursor layer, and a Zn precursor layer, respectively (S3); And (S4) forming a light absorbing layer by heat-treating the deposited metal precursor under a sulfided or selenized gas atmosphere, wherein step (S3) first deposits a Zn precursor layer on the first electrode. And depositing a metal precursor such that both sides of the Cu precursor layer are adjacent to the Sn precursor layer, and at least one side of the Sn precursor layer is adjacent to the Zn precursor layer.

Description

CZTS thin film solar cell comprising a light absorption layer of uniform composition and a method for manufacturing thereof {A SOLAR CELL COMPRISING CZTS THIN FILM WITH UNIFORM COMPOSITION AND A METHOD OF MANUFACTURING THE SAME}

The present invention relates to a CZTS thin film solar cell and a method for manufacturing the same, and more particularly, to a CZTS thin film type solar cell including a light absorption layer having a uniform composition.

Chalcoprite-based solar cell technology is likely to achieve high efficiency among all thin film solar cell technologies. The thin film solar cell includes CuInSe ₂ , CuInS ₂ , Cu (In, Ga) Se _2, and the like. However, due to the limitations of limited reserves of indium (In) and the problem of expensive materials, solar cells made of such a composition have difficulty in implementing low-cost thin film solar cells.

One alternative solution to this problem is a thin film solar cell including a CZTS (Cu ₂ ZnSn (S, Se) ₄ ) -based light absorption layer. CZTS-based solar cells are easy to implement low-cost solar cells because the material constituting the absorption layer is very widely present on the earth. However, in order to manufacture a CZTS-based light absorbing layer of a conventional thin film solar cell, Cu, Zn and Sn are sequentially deposited to form a copper zinc tin (CuZnSn) precursor, and then selenium or sulfur is deposited on the CuZnSn precursor. ), And heat-treated to form a light absorption layer of CZTS (Cu ₂ ZnSn _Sn S ₄ ) or CZTSe (Cu ₂ ZnSnSe ₄ ).

However, when the CZTS-based light absorbing layer is manufactured by the conventional method, the composition of the light absorbing layer becomes uneven after heat treatment, resulting in a marked decrease in cell efficiency due to the difference in the band gap inside. In addition, the nonuniform composition of the light absorption layer makes the absorption wavelength of the irradiated light non-uniform, making it difficult to implement a stable thin film solar cell. Therefore, in order to solve the said problem and to improve the efficiency of a thin film solar cell, the manufacturing method which can equalize the composition of a light absorption layer is calculated | required.

An object of the present invention is to provide a method for producing a CZTS light absorbing layer having a uniform composition distribution and uniform crystallinity.

Still another object of the present invention is to provide a CZTS thin film solar cell having excellent light conversion efficiency.

One embodiment of the present invention provides a method for manufacturing a CZTS-based thin film solar cell, the method comprising the steps of preparing a substrate (S1); Forming a first electrode on the substrate (S2); Depositing a Cu precursor, a Sn precursor, and a Zn precursor on the first electrode to form two or more Cu precursor layers, a Sn precursor layer, and a Zn precursor layer, respectively (S3); And heat treating the deposited metal precursor layer under a sulfided or selenized gas atmosphere to form a light absorbing layer (S4). In this case, in the step (S3), the Zn precursor layer is first deposited on the first electrode, and both surfaces of the Cu precursor layer are adjacent to the Sn precursor layer, and at least one surface of the Sn precursor layer is adjacent to the Zn precursor layer. The precursor layer is deposited.

In one embodiment of the invention, the metal precursor is on the first electrode

(First electrode) -Zn-Sn-Cu-Sn-Zn-Sn-Cu precursor; (First electrode) -Zn-Sn-Cu-Sn-Zn-Sn-Cu-Sn-Zn-Sn-Cu precursor; Or (first electrode) -Zn-Sn-Cu-Sn-Zn-Sn-Cu-Sn-Zn-Sn-Cu-Sn-Zn-Sn-Cu precursor in order.

In one embodiment of the present invention, the thickness of the light absorption layer may be 0.3μm to 2μm.

In one embodiment of the present invention, the light absorption layer may be a quaternary compound of Cu ₂ ZnSn (S, Se) ₄ .

In one embodiment of the present invention, the first electrode may be a molybdenum (Mo) thin film.

In one embodiment of the present invention, the metal precursor may be deposited by a sputtering process.

In one embodiment of the present invention, the method comprises the steps of forming a buffer layer on the light absorbing layer (S5); Forming a window layer on the buffer layer (S6); And forming a second electrode on the window layer (S7).

Another embodiment of the present invention provides a CZTS-based thin film solar cell manufactured according to the method.

One embodiment of the present invention provides a method for producing a CZTS thin film having excellent surface roughness, uniform composition, high film density and large grains. According to the above manufacturing method, a large-area CZTS thin film can be manufactured, and the existing manufacturing process can be simplified and the process cost can be reduced.

Figure 1 shows an embodiment of a thin film solar cell manufacturing process flow chart.
2 is a cross-sectional view of an embodiment of a thin film solar cell in which a metal precursor is deposited on a first electrode.
3 is a cross-sectional view of another embodiment of a thin film solar cell in which a metal precursor is deposited on a first electrode.
4 is a cross-sectional view of an embodiment of a thin film solar cell having a light absorption layer formed after a sulfidation or selenization process.
Figure 5 shows the SEM photograph of the light absorption layer of the thin film solar cell prepared in the embodiment.
6 shows another embodiment of a process chart of manufacturing a thin film solar cell.

Hereinafter, the embodiment of the present invention will be described in detail. However, the following embodiments are presented by way of illustration of the present invention, whereby the present invention is not limited and the present invention is capable of various modifications and applications within the scope of the claims to be described later and equivalents interpreted therefrom. .

One embodiment of the present invention provides a method for manufacturing a CZTS-based thin film solar cell.

The CZTS thin film means a thin film including Cu, Zn, Sn and S or Se, and the CZTS-based thin film solar cell manufacturing method may include the following steps:

Preparing a substrate (S1);

Forming a first electrode on the substrate (S2);

Depositing a Cu precursor, a Sn precursor, and a Zn precursor on the first electrode to form two or more Cu precursor layers, a Sn precursor layer, and a Zn precursor layer, respectively (S3); And

Heat-treating the deposited metal precursor in a sulfided or selenized gas atmosphere to form a light absorption layer (S4).

At this time, in the step (S3) the metal precursor is deposited in a specific order, in one embodiment of the present invention, after the Zn precursor layer is deposited on the first electrode, both sides of the Cu precursor layer and the Sn precursor layer Adjacent metal layers may be deposited in an order in which at least one surface of the Sn precursor layer is adjacent to the Zn precursor layer.

Hereinafter, each step will be described in detail. On the other hand, it will be described with reference to Figures 1 to 6 attached to the present invention to more easily understand the manufacturing method of the thin film solar cell of the present invention.

Figure 1 shows an embodiment of a thin film solar cell manufacturing process flow chart.

In one embodiment of the present invention, the manufacturing process of the thin film solar cell comprises the steps of preparing a substrate (S1), forming a first electrode (S2), depositing a metal precursor on the first electrode (S3) And sulfiding or selenizing heat-treating the deposited metal precursor layer (S4).

Figure 2 shows a cross-sectional view of one embodiment of a thin film solar cell.

In one embodiment of the present invention, the thin film solar cell may use glass, ceramic or metal as the substrate 100 in step (S1) of preparing the substrate.

In an embodiment of the present invention, in the forming of the first electrode (S2), a molybdenum (Mo) thin film may be used as the first electrode 200 formed on the substrate 100. Molybdenum (Mo) is excellent in electrical conductivity, ohmic contact, high temperature stability, the molybdenum (Mo) thin film is formed by the sputtering process, it can be deposited by other processes of the foil.

In an embodiment of the present invention, in the deposition of the metal precursor (S3), the metal precursor layers 301, 302, and 303 are deposited on the first electrode 200 to form the light absorption layer 300. . In one embodiment of the present invention, after depositing a Cu precursor, a Sn precursor and a Zn precursor on the first electrode 200, a sputtering process may be performed to continuously form a multilayer metal precursor layer. In addition to the sputtering process, it is also possible to deposit a metal precursor using an evaporation process, but the sputtering process is more preferable for producing a thin film solar cell having excellent reproducibility and a large area.

In one embodiment of the present invention, each of the metal precursor layers includes two or more Cu precursor layers 303, Sn precursor layers 302, and Zn precursor layers 301. At this time, the Cu precursor layer 303, the Sn precursor layer 302 and the Zn precursor layer 301 are deposited in a specific order. Specifically, after depositing a Zn precursor layer on the first electrode first, both surfaces of the Cu precursor layer is adjacent to the Sn precursor layer, and at least one surface of the Sn precursor layer is to be deposited to be adjacent to the Zn precursor layer. In this case, the distribution of the light absorbing layer becomes more uniform.

2 and 3, which are embodiments of the present invention, the plurality of metal precursor layers 301, 302, and 303 may be deposited on the first electrode in the following order.

(First electrode) -Zn-Sn-Cu-Sn-Zn-Sn-Cu precursor;

(First electrode) -Zn-Sn-Cu-Sn-Zn-Sn-Cu-Sn-Zn-Sn-Cu precursor; or

(First electrode) -Zn-Sn-Cu-Sn-Zn-Sn-Cu-Sn-Zn-Sn-Cu-Sn-Zn-Sn-Cu precursor.

In one embodiment of the present invention, the total thickness of the metal precursor layer (301, 302, 303) formed through the step (S3) is 300 to 1200nm, preferably 400 to 800nm. When having the numerical range, the total thickness of the light absorption layer generated after the heat treatment may be in the range of 0.3 to 2㎛.

Unlike the conventional method of sputtering by sequentially depositing a Zn precursor layer, a Sn precursor layer, and a Cu precursor layer on the first electrode, two or more Zn precursor layers, two or more Sn precursor layers, and two or more Cu precursor layers are deposited in a specific order. Subsequently, in the case of sulfidation or selenization heat treatment, a light absorption layer of a more uniform and dense CZTS-based thin film solar cell may be manufactured. As a result, the cell efficiency is improved due to the band gap difference of the thin film solar cell.

The composition of Cu with respect to the total amount of the metal precursor layer may be 25 to 75 at%, preferably 37.5 to 62.5 at%. The composition of Zn with respect to the total amount of the metal precursor layer may be 12.5 to 37.5 at%, preferably 17.5 to 32.5 at%. The composition of Sn relative to the total amount of the metal precursor layer may be 12.5 to 37.5 at%, preferably 17.5 to 32.5 at%.

In an embodiment of the present invention, in the step of selenization or sulfidation heat treatment (S4), selenium vapor or sulfur vapor is supplied to the substrate on which the metal precursor layers 301, 302, and 303 formed in the previous step are heat treated. At this time, the fusion cell temperature of selenium or sulfur is preferably adjusted so that the deposition rate is 5-60 Å / s at room temperature. When performing the selenization or sulfiding, the substrate temperature is preferably performed for 0.1 to 3 hours while maintaining in the 400 to 600 ℃ range. This is because impurities may be severely formed at 400 ° C. or lower, and it is difficult to suppress Sn loss at 600 ° C. or higher, and thus it is difficult to obtain a thin film having a suitable composition.

The selenization or sulfidation treatment can be carried out in a furnace, simultaneous evaporation equipment or RTA (RapidThermal Annealing) equipment, in addition to all the sulfide / selenization heat treatment equipment possible within the scope of the present invention can be applied.

The metal precursor layer may be a light absorption layer generated through a heat treatment process may be a quaternary compound of Cu ₂ ZnSn (S, Se) ₄ .

As shown in Figure 6, one embodiment of the present invention, in addition to the above (S1) to (S4), forming a buffer layer on the formed light absorption layer (S5); Forming a window layer on the buffer layer (S6); And forming a second electrode on the window layer (S7).

Yet another embodiment of the present invention provides a CZTS-based thin film solar cell manufactured by the above-described manufacturing method. In one embodiment, the efficiency of the CZTS-based thin film solar cell may be 2 to 8%.

Hereinafter, the present invention will be described through more specific examples.

Example : Fabrication of thin film solar cell

First, the molybdenum back electrode 200 was deposited on the soda lime glass substrate 100 by a DC sputtering method to a thickness of about 500 nm.

Subsequently, CZT-based precursor thin films were formed by sputtering Sn, Zn, and Cu on the back electrode 200 in the order shown in FIG. 3. The thickness of the formed precursor layer is shown in Table 1 below, and the total thickness of the precursor layer was about 442 nm.

Metal precursor Deposition time [sec] Thickness [nm] Cu 184 53.290583  SnS 87 61.43762 ZnS 253 59.440186  SnS 58 40.958413 Cu 123 35.527056  SnS 145 102.39603 ZnS
(Deposited directly above the first electrode) 379 89.160278 Total metal precursor layer thickness [nm]
442.210

Next, the CZT-based thin film was sulfided by supplying sulfur vapor at a substrate temperature of 430 ° C. for 2 hours to complete a Cu ₂ ZnSnS ₄ thin film (FIG. 4). At this time, sulfidation was carried out in a simultaneous vacuum evaporation apparatus in which the vacuum evaporation process was performed, and the temperature of the fusion cell was set at 140 ° C. After the heat treatment, the thickness of the formed light absorbing layer was 635 nm.

Figure 5 shows a SEM photograph of the light absorption layer of the thin film solar cell prepared in Preparation Example 1. After the heat treatment, a 130-nm-thick Mo-S layer (a mixed compound of Mo and S) was formed between the first electrode Mo and the light absorption layer CZTS, and the light absorption layer had uniform crystallinity and large crystal grains. Had

Experimental Example : Thin film solar cell Light conversion  Efficiency evaluation

Using a CZTS-based thin film manufactured according to an embodiment of the present invention, by forming a 60nm CdS buffer layer 400, a 400nm ZnO window layer 500 and an Al electrode 600 formed thereon, to complete a CZTS-based thin film solar cell It was.

Although the invention has been described with reference to the embodiments shown in the drawings, these are merely exemplary and those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

100: substrate
200: first electrode
300: light absorption layer
301: Zn precursor layer
302: Sn precursor layer
303 Cu precursor layer
400: buffer layer
500: window layer
600: second electrode

Claims (8)

As a method of manufacturing a CZTS-based thin film solar cell, the method
Preparing a substrate (S1);
Forming a first electrode on the substrate (S2);
Depositing a Cu precursor, a Sn precursor, and a Zn precursor on the first electrode to form two or more Cu precursor layers, a Sn precursor layer, and a Zn precursor layer, respectively (S3); And
And heat treating the deposited metal precursor layer under a sulfided or selenized gas atmosphere to form a light absorbing layer (S4),
In the step (S3), a Zn precursor layer is first deposited on the first electrode, and both surfaces of the Cu precursor layer are adjacent to the Sn precursor layer, and at least one surface of the Sn precursor layer is adjacent to the Zn precursor layer. And depositing a metal precursor layer. The method of claim 1,
The metal precursor is deposited on the first electrode in the following order:
(First electrode) -Zn-Sn-Cu-Sn-Zn-Sn-Cu precursor;
(First electrode) -Zn-Sn-Cu-Sn-Zn-Sn-Cu-Sn-Zn-Sn-Cu precursor; or
(First electrode) -Zn-Sn-Cu-Sn-Zn-Sn-Cu-Sn-Zn-Sn-Cu-Sn-Zn-Sn-Cu precursor. The method according to claim 1 or 2,
The thickness of the light absorption layer is characterized in that 0.3μm to 2μm, method. The method according to claim 1 or 2,
The light absorption layer is a quaternary compound of Cu ₂ ZnSn (S, Se) ₄ . The method according to claim 1 or 2,
Wherein said first electrode is a molybdenum (Mo) thin film. The method according to claim 1 or 2,
The metal precursor is deposited by a sputtering process. The method according to claim 1 or 2,
Forming a buffer layer on the light absorbing layer (S5);
Forming a window layer on the buffer layer (S6); And
And forming a second electrode on said window layer (S7). delete

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