KR20170036617A - Method for manufacturing CZTS or CZTSe thin film by simultaneous evaporation method and solar cell manufactured therefrom - Google Patents

Abstract

The present invention relates to a thin film having a bandgap slope and a thin film solar cell using the thin film solar cell, wherein the CZTS-based precursor is formed by simultaneous evaporation and the VI group element is supplied and simultaneously subjected to rapid thermal annealing under an inert gas atmosphere. A method of manufacturing a solar cell includes: preparing a substrate; Forming a back electrode on the substrate; Depositing a metal precursor including a Cu precursor, a Zn precursor, a Sn precursor and a VI group element precursor on the rear electrode to form a metal precursor layer; And a heat treatment in an inert gas atmosphere to produce a light absorbing layer.

Description

[0001] The present invention relates to a method for producing a CZTS or CZTSe thin film using a simultaneous evaporation method, and a solar cell prepared from the same,

The present invention relates to a method for producing a CZTS or CZTSe thin film using a simultaneous evaporation method and a solar cell produced therefrom.

Recently, as interest in environmental problems and depletion of fossil resources has been amplified, researches on renewable energy fields such as wind power, hydro power, fuel cell, and solar cell are being actively carried out. Particularly, interest in solar power generation that can be used semi-permanently is increasing significantly. Most of the solar cells used in the early solar power generation were manufactured using crystalline silicon, but the cost of producing solar cells of several hundreds of micrometers thickness accounted for a considerable portion of the total production cost, However, interest in thin film solar cells is increasing.

Thin-film solar cells have advantages of cost reduction and continuous process by using a thin film of several μm thickness as an absorption layer, and it is possible to use various substrates such as glass and metal to develop an integrated solar cell module and a flexible solar cell . In recent years, CIGS (gallium arsenide) using copper (Cu), indium (In), gallium (Ga), sulfur (S) or selenium (Se), which has high efficiency, long term stability, Based thin film solar cell has been actively studied. However, as the amount of rare earth resources such as indium and gallium required for the CIGS-based absorption layer is small and the price of raw materials surges, the manufacturing cost of the CIGS-based solar cell is increased, and the marketability is limited.

Accordingly, research on CZTS thin film solar cells using zinc (Zn) and tin (Sn) instead of indium and gallium as low-cost materials has attracted attention. CZTS thin film solar cells using copper (Cu), zinc (Zn), tin (Sn), sulfur (S) or selenium (Se) can be manufactured by first sputtering the precursor on a substrate by sputtering, simultaneous evaporation, Followed by post-heat treatment by various methods. Particularly, in the case of the five-membered compound CZT (S, Se), the post-heat treatment is mainly performed by supplying a VI group element such as selenium or sulfur to the first heat treatment, and then S or Se is additionally supplied to perform the second heat treatment The process time is long and the continuous process is difficult. In addition, it is difficult to control the inflow amount of selenium or sulfur in the heat treatment process of the absorbent layer, and there are many problems in reproducibility. Therefore, it is necessary to develop a technique to shorten the processing time for the thin film enhancement.

Recently, the band gap slope was applied in a CIG (S, Se) thin film by sulfiding the surface of CIGS using the property of controlling the bandgap of CIGS by controlling the ratio of Se / [Se + S] A method of improving the efficiency of CIG (S, Se) thin film solar cells through a grading structure has been applied. The S / [Se + S] ratio of the CZT (S, Se) thin film solar cell can be improved by increasing the charge carrier collection efficiency and improving the electrical characteristics of the device when the bandgap inclination is formed in the thin film. It is possible to control the band gap.

Therefore, there is a need to develop a manufacturing technique of a good quality CZT (S, Se) thin film solar cell absorbing layer by shortening the process time and forming the band gap slope as described above.

Korean Patent Publication No. 10-2015-0051164

Accordingly, the present invention has been completed by establishing a CZT (S, Se) thin film and a method of manufacturing a solar cell using the same, which can shorten the process time and have a bandgap gradient.

Therefore, an object of the present invention is to provide a method of manufacturing a CZTS thin film solar cell using simultaneous evaporation method in which selenium is added to a metal precursor so as to have a band gap slope and a rapid thermal annealing is performed under an inert gas.

Another object of the present invention is to provide a CZT (S, Se) based solar cell manufactured by the method of the present invention.

Accordingly, the present invention provides a method of manufacturing a semiconductor device, comprising: preparing a substrate; Forming a back electrode on the substrate; Depositing a metal precursor including a Cu precursor, a Zn precursor, a Sn precursor and a VI group element precursor on the rear electrode to form a metal precursor layer; And a heat treatment in an inert gas atmosphere to produce a light absorbing layer. The present invention also provides a method of manufacturing a CZTS thin film solar cell using a simultaneous evaporation method.

In one embodiment of the present invention, the original consumption of [VI group element] / [Cu + Zn + Sn] in the deposited metal precursor layer may be 1.2 to 2.0.

In one embodiment of the present invention, the [Cu] / [Zn + Sn] source consumption in the deposited metal precursor layer may be 0.6 to 0.95.

In one embodiment of the present invention, the elemental consumption of [Zn] / [Sn] in the deposited metal precursor layer may be 1.0 to 1.4.

In one embodiment of the present invention, the VI group element may be selenium (Se).

In one embodiment of the present invention, the inert gas may be at least one of argon and hydrogen sulfide.

In one embodiment of the present invention, the inert gas is a mixed gas of argon and hydrogen sulfide, and hydrogen sulfide based on 100% of the mixed gas may be contained in the mixed gas at a concentration of 1 to 20%.

In one embodiment of the present invention, the heat treatment may be a heat treatment at a pressure of 500 to 800 Torr and a temperature of 400 to 500 ° C for 1 minute to 10 minutes.

In one embodiment of the present invention, the rear electrode may be molybdenum.

In one embodiment of the present invention, the light absorption layer may be a CZTS or CZTSe series light absorption layer.

The present invention also provides a CZT (S, Se) solar cell manufactured by the method of the present invention.

Unlike the post-heat treatment method for forming a light absorbing layer of a conventional CZT (S, Se) solar cell, the present invention forms a precursor layer containing selenium (Se) and rapidly heat- The manufacturing process of the battery can be simplified, and the solar cell manufactured by the manufacturing method of the present invention has an increased ratio of S / [Se + S] toward the surface of the absorbing layer after heat treatment to form a band gap slope, .

FIG. 1 is a schematic diagram of a CZTS precursor (a) and a heat treatment (b) deposited by the simultaneous evaporation method according to the present invention.
2 shows the composition ratio of the absorbent layer prepared by heat treatment under different temperature conditions.
Figure 3 shows the surface Raman spectrum of the absorbent layer prepared by heat treating at different temperature conditions.
FIG. 4 shows the electrical characteristics of a CZT (S, Se) thin film solar cell annealed at different temperature conditions.
5 shows the distribution of the cross-section (a) and the metal precursor composition (b) of a CZT (S, Se) thin film prepared by the method of the present invention.
6 shows the results of current density analysis of CZT (S, Se) thin film solar cells and control solar cells according to the voltage of the present invention.

Generally, a method of manufacturing a CZTS thin film solar cell is a method in which a metal precursor is deposited on a substrate, and then a first heat treatment is performed at a high temperature and then a second heat treatment is performed again, have.

Further, it is difficult to control the inflow amount of selenium or sulfur in the heat treatment process of the absorbent layer, and the reproducibility is also bad.

Accordingly, the present invention provides a method for solving such a problem, comprising the steps of: depositing a metal precursor on a substrate by simultaneous evaporation including selenium, which is a certain amount of Group VI element in forming a precursor layer; and performing a rapid thermal annealing process under an inert gas (S, Se) thin film solar cell absorbing layer having excellent characteristics of a thin film and having a band gap slope, and a method of manufacturing a CZT (S, Se) thin film solar cell including the same.

Therefore, the present invention can provide a method of manufacturing a CZT (S, Se) based absorption layer having a band gap slope, and further, the present invention provides a method of manufacturing a CZT (S, Se) Forming a back electrode on the substrate; Depositing a metal precursor including a Cu precursor, a Zn precursor, a Sn precursor and a VI group element precursor on the rear electrode to form a metal precursor layer; And a heat treatment in an inert gas atmosphere to produce a light absorbing layer. The present invention also provides a method for manufacturing a CZTS thin film solar cell.

In particular, the metal precursor deposits copper, zinc, tin, selenium or sulfur within the deposited precursor layer at a constant rate.

After the metal precursor layer is formed, a light absorbing layer is prepared by heat treatment in an inert gas atmosphere, and then the buffer layer, the front electrode layer, and the upper electrode are deposited in the same manner as the general thin film solar cell process, do.

In the present invention, the original consumption of [VI group element] / [Cu + Zn + Sn] in the heat-treated metal precursor layer is 1.2 to 2.0, the [Cu] / [Zn + Sn] source consumption is 0.6 to 0.95, Zn] / [Sn] is in the range of 1.0 to 1.4.

Particularly, the elemental ratio of [VI group element] / [Cu + Zn + Sn] in the CZTS light-absorbing layer precursor is preferably 1.2 or more. When the ratio of the VI group element is higher than 1.2 range, the crystallinity is improved, This is because it has the advantage of being dissolved. The original consumption of [Cu] / [Zn + Sn] in the CZTS-based light absorbing layer precursor may be 0.6 to 0.95, preferably 0.7 to 0.95 because if the ratio of copper is higher than the above range, And there may be a problem of a high resistance if it is lower than the above numerical range. The original consumption of [Zn] / [Sn] in the metal precursor may be 1.0 to 1.4, preferably 0.8 to 1.4. When the ratio of zinc is higher than the above range, crystallinity decreases and resistance increases And if it is lower than the above numerical range, there may be a problem of deterioration in crystallinity and high resistance.

The Group VI element may be selenium (Se), and the inert gas may be at least one gas selected from the group consisting of argon and hydrogen sulfide.

Preferably, the inert gas may be a mixed gas of argon and hydrogen sulfide. The hydrogen sulfide may be used at a concentration of 1 to 20% (volume%) based on 100% of the total gas mixture. For example, a concentration of 10% hydrogen sulfide means that hydrogen sulfide is present at a concentration of 10% in a mixed gas of 90% argon and 10% hydrogen sulfide.

The heat treatment may be a rapid thermal annealing at a pressure of 500 to 800 Torr and a temperature of 400 to 500 ° C for 1 minute to 10 minutes. If the pressure is lower than the above-described range, or the temperature is low or the time is short, the crystallization is not properly performed and the efficiency is low. If the pressure, temperature or time exceeds the above range, And this can also result in low efficiency.

Further, the rear electrode may be molybdenum, and the light absorbing layer manufactured by the above method may be a light absorbing layer of CZTS or CZTSe series.

Further, the present inventors analyzed whether the CZT (S, Se) -based solar cell of the present invention produced by the above-mentioned method has excellent efficacy.

As a result, the ratio of S / [Se + S] of CZT (S, Se) films increased after annealing, and that of CZT (S, Se) (S, Se) -based absorption layer having a slope at which the bandgap decreases from that of the CZT.

Accordingly, the present invention can provide a CZT (S, Se) thin film solar cell having improved electrical characteristics.

Hereinafter, the present invention will be described in detail with reference to examples. However, these examples are intended to further illustrate the present invention, and the scope of the present invention is not limited to these examples.

≪ Example 1 >

Thin Film Absorption Layer of CZT (S, Se) by Metal Heat Treatment Process and Fabrication of Solar Cell Using It

Molybdenum (Mo) was deposited on a soda lime glass substrate using a sputtering (DC magnetron sputtering) method. The CZTS thin film solar cell precursors were deposited on molybdenum-coated soda lime glass substrates using Cu-Zn, Sn, and Se as co-evaporators. At this time, the deposition of the metal precursor was carried out in the order of Mo / Cu-Zn-Sn / Se as shown in FIG. 1 (a), and the above precursors were deposited at room temperature. Then, the metal precursor deposited as shown in FIG. 1 (b) was placed in the rapid thermal annealing chamber, the chamber was evacuated to a vacuum of 3 mTorr or less by using a rotary pump, and then a mixed gas of argon and hydrogen sulfide was used The pressure in the chamber was adjusted to 600 torr by injecting the hydrogen sulfide in the mixed gas so that the concentration of hydrogen sulfide was 10% (that is, a mixture gas of 90% argon and 10% hydrogen sulfide was used) and then 420, 440, 460, And then heat-treated at 500 DEG C for 4 minutes to prepare a light absorbing layer.

After the formation of the light absorbing layer, the CZT (S, Se) solar cell of the present invention was fabricated by depositing a buffer layer, a front electrode layer, and an upper electrode in a subsequent process as a general solar cell manufacturing method.

≪ Example 2 >

Analysis of Characteristics of CZT (S, Se) Solar Cells Fabricated by Metal Heat Treatment Process

The inventors analyzed the composition ratio of the metal precursors in the absorption layer formed on the substrate in the above Example 1 and the surface analysis of the absorption layer.

As a result of the analysis, the composition ratio of the deposited precursor was in the range of 0.6 to 0.9 for [Cu] / [Zn + Sn], 1.0 to 1.4 for [Zn] / [Sn] ] Was 1.2 to 2.0, and as shown in FIG. 2 and FIG. 3, the S / [Se + S] ratio was increased as the temperature increased.

As a result of analyzing the electrical characteristics of the manufactured solar cell, it was found that the electrical characteristics were excellent as shown in Fig. 4, and the distribution of composition ratios of copper, zinc, tin, selenium and sulfur according to the cross- The ratio of S / [Se + S] increases with increasing distance to the surface of the absorber, indicating that the bandgap slope is well formed inside the single layer of the absorber layer.

Further, in order to confirm the excellent performance of the solar cell manufactured according to the present invention, the present inventors analyzed the current density according to the voltage of a conventional CZTSe solar cell and a CZTSSe solar cell according to the present invention. The conventional CZTSe solar cell used as a control was a CZTS thin film solar cell precursor, which was coated with molybdenum-coated soda lime glass substrate on four metal elements of Cu, Zn, Sn and Se by using a co-evaporator Lt; / RTI > The metal precursors were deposited in the order of Mo / Cu-Zn-Sn / Se. Then, the deposited metal precursor was placed in the rapid thermal annealing chamber and the chamber was evacuated to a vacuum of 3 mTorr or less And then argon was injected to adjust the pressure inside the chamber to 600 torr and then heat treatment was carried out at 480 ° C. for 4 minutes to prepare a light absorbing layer and a solar cell manufactured using the same was used.

As a result of the analysis, it was confirmed that the CZTSSe solar cell according to the present invention had improved electrical characteristics and increased efficiency as compared with the conventional CZTSe solar cell, as shown in FIG.

The present invention has been described with reference to the preferred embodiments. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present invention is defined by the appended claims rather than by the foregoing description, and all differences within the scope of equivalents thereof should be construed as being included in the present invention.

Claims (11)

Preparing a substrate;
Forming a back electrode on the substrate;
Depositing a metal precursor including a Cu precursor, a Zn precursor, a Sn precursor and a VI group element precursor on the rear electrode to form a metal precursor layer; And
And a heat treatment in an inert gas atmosphere to produce a light absorbing layer, wherein the CZTS thin film solar cell is manufactured by the simultaneous evaporation method. The method according to claim 1,
Wherein a source consumption of [VI group element] / [Cu + Zn + Sn] in the deposited metal precursor layer is 1.2 to 2.0. The method according to claim 1,
Wherein the [Cu] / [Zn + Sn] source consumption in the deposited metal precursor layer is 0.6 to 0.95. The method according to claim 1,
Wherein the original consumption of [Zn] / [Sn] in the deposited metal precursor layer is 1.0 to 1.4. The method according to claim 1,
Wherein the Group VI element is selenium (Se). The method according to claim 1,
Wherein the inert gas is at least one gas selected from the group consisting of argon and hydrogen sulfide. The method according to claim 6,
Wherein the inert gas is a mixed gas of argon and hydrogen sulfide, and hydrogen sulfide is contained in the mixed gas at a concentration of 1 to 20% based on 100% of the mixed gas. The method according to claim 1,
Wherein the heat treatment is performed at a pressure of 500 to 800 Torr and a temperature of 400 to 500 占 폚 for 1 minute to 10 minutes. The method according to claim 1,
Wherein the back electrode is molybdenum. The method according to claim 1,
Wherein the light absorption layer is a CZTS or CZTSe series light absorption layer. A CZT (S, Se) based thin film solar cell produced by any one of claims 1 to 10.

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