KR101787625B1 - Method of manufacturing Zn(O,S) thin film - Google Patents

Abstract

The present invention provides a method for preparing a zinc precursor solution, comprising: preparing a solution containing a zinc precursor solution, a sulfur precursor solution and a hydroxide ion, respectively; Mixing the zinc precursor solution, the sulfur precursor solution and the solution containing hydroxide ions in a micro reactor to prepare a mixture; Continuously supplying the mixture onto the substrate using a spin coating method so that the mixture can be continuously formed on the substrate, and impinging the mixture on the substrate to form a thin film; And annealing the thin film. The present invention also provides a method of manufacturing a Zn (O, S) thin film.

Description

[0001] The present invention relates to a Zn (O, S) thin film,

The present invention relates to a method of manufacturing a thin film, and more particularly, to a method of manufacturing a Zn (O, S) thin film.

In the field of solar cell, there is a need to develop a solution process technology for depositing a zinc sulfide thin film instead of a cadmium sulfide thin film in preparation for the regulation of use of cadmium which is harmful heavy metal. Conventional solution deposition processes for forming a thin film have disadvantages in that they can not control the band gap of the zinc sulfide thin film and the deposition time of the zinc sulfide thin film is long and economic and time loss is large and the continuous process is impossible and commercialization is difficult have. In addition, for example, since the temperature at which the zinc sulfide thin film is formed is higher than the CIGS light absorption layer thin film forming temperature of the CIGS thin film solar cell of the compound thin film solar cell, the application of the zinc sulfide thin film to the CIGS compound thin film solar cell It is necessary to develop a solution process for lowering the heat treatment temperature of the zinc sulfide thin film.

It is an object of the present invention to provide a method of manufacturing a Zn (O, S) thin film capable of controlling a band gap by a low temperature process, which solves various problems including the above problems. However, these problems are exemplary and do not limit the scope of the present invention.

According to one aspect of the present invention, a method of manufacturing a Zn (O, S) thin film is provided. The method for producing the Zn (O, S) thin film includes: preparing a solution containing a hydroxide ion, a zinc precursor solution and a sulfur precursor solution, respectively; Preparing a solution containing the hydroxide ion, mixing the zinc precursor solution and the sulfur precursor solution in a micro reactor to prepare a mixture; Continuously supplying the mixture onto the substrate using a spin coating method so that the mixture can be continuously formed on the substrate, and impinging the mixture on the substrate to form a thin film; And heat treating the thin film.

In the Zn (O, S) method of manufacturing a thin film, a solution containing the hydroxide ions are at least one of a sodium hydroxide (NaOH), ammonium hydroxide (NH ₄ OH) and ammonium acetate (NH ₄ CH ₃ CO ₂₎ And may be formed by dissolving in a solvent.

The zinc precursor solution may be selected from the group consisting of zinc sulfate hepta-hydrate (ZnSO ₄ .7H ₂ O), zinc sulfate (ZnSO ₄ ), zinc chloride (ZnCl ₂ ) May be formed by dissolving at least one of zinc nitrate (Zn (NO ₃ ) ₂ ) and zinc acetate dihydrate ((CH ₃ COO) ₂ Zn · 2H ₂ O) in a solvent.

In the above method for producing a Zn (O, S) thin film, the sulfur precursor solution may contain at least one of thiourea (CH ₄ N ₂ S), sodium thiosulfate (Na ₂ S ₂ O ₃ ), sodium sulfide (Na ₂ S) (H ₂ S) may be dissolved in a solvent.

According to another aspect of the present invention, a method of manufacturing a Zn (O, S) thin film is provided. The Zn (O, S) method of manufacturing a thin film of zinc sulfate monohydrate (zinc sulfate hepta-hydrate, ZnSO 4 · 7H 2 O), Bang urea _{(thiourea, CH 4 N 2 S} ) , and ammonium acetate (ammonium acetate, NH ₄ CH ₃ CO ₂ ) in water to prepare a mixture by mixing the precursor solution in a micro reactor; Continuously supplying the mixture onto the substrate using a spraying method so that the mixture can be continuously formed on the substrate, wherein the mixture is sprayed onto the substrate to form a thin film; And heat treating the thin film.

The concentration of the zinc sulfate hepta-hydrate (ZnSO ₄ .7H ₂ O), the concentration of the thiourea (CH ₄ N ₂ S) and the concentration of the zinc sulfate hepta-hydrate The concentration of ammonium acetate (NH ₄ CH ₃ CO ₂ ) is approximately 0.05 M, 0.066 M and 0.012 M, respectively, in 100 ml of water, the flow rate of the mixture in the microreactor is approximately 0.1 liter / min, The rotational speed of the spin coater to be mounted is approximately 1500 rpm, and the time for which the mixture collides with the substrate may be approximately 2 minutes.

In the method of manufacturing the Zn (O, S) thin film, the step of heat-treating the thin film may include heat treating the thin film at about 200 ° C under atmospheric pressure for about 30 minutes.

According to one embodiment of the present invention as described above, the deposition time is shortened by depositing a Zn (O, S) thin film at a low temperature using a continuous flow reaction (CFR) spin coating method and the band gap engineering Cd-free Zn (O, S) thin film can be realized with low cost and low heat treatment temperature. Of course, the scope of the present invention is not limited by these effects.

FIG. 1 is a graph illustrating the light transmittance of a Zn (O, S) thin film implemented in a manufacturing method according to an embodiment of the present invention.
FIG. 2 is a graph showing the XRD analysis results of the Zn (O, S) thin film implemented by the manufacturing method according to an embodiment of the present invention.
FIGS. 3A to 3C are graphs showing XPS analysis results of a Zn (O, S) thin film implemented by a manufacturing method according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, Is provided to fully inform the user. Also, for convenience of explanation, the components may be exaggerated or reduced in size.

It is to be understood that throughout the specification, when an element such as a film, an area, or a substrate is referred to as being "on" another element, the element may be directly "on" another element, It is to be understood that there may be other components intervening in the system. On the other hand, when an element is referred to as being "directly on" another element, it is understood that there are no other elements intervening therebetween. Like numbers refer to like elements. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items.

Also, relative terms such as "top" or "bottom" may be used herein to describe the relationship of certain elements to other elements as illustrated in the figures. Relative terms are intended to include different orientations of the device in addition to those depicted in the Figures. For example, in the figures the elements are turned over so that the elements depicted as being on the top surface of the other elements are oriented on the bottom surface of the other elements. Thus, the example "top" may include both "under" and "top" directions depending on the particular orientation of the figure. If the elements are oriented in different directions (rotated 90 degrees with respect to the other direction), the relative descriptions used herein can be interpreted accordingly.

A method of preparing a Zn (O, S) thin film according to an embodiment of the present invention includes preparing a solution containing a hydroxide ion, a zinc precursor solution and a sulfur precursor solution, respectively (S10); (S20) mixing the solution containing the hydroxide ions, the zinc precursor solution and the sulfur precursor solution in a micro reactor to prepare a mixture; (S30) a step of forming a thin film by continuously supplying the mixture onto the substrate by using a spin coating method so that the mixture can be continuously formed on the substrate, ; And heat treating the thin film (S40). The Zn (O, S) thin film used in this specification can be understood as a zinc thin film containing sulfur and oxygen.

In the method of manufacturing the Zn (O, S) thin film, a substrate can be prepared first. The substrate may be, for example, Soda Lime Glass. Soda lime glass substrates can be cleaned using heated sodium hydroxide solution. Further, the soda lime glass substrate cleaned with ultrapure water may be further washed with ultrasonic waves.

On the other hand, a zinc precursor solution can be formed by dissolving a zinc source and ammonium hydroxide (NH ₄ OH) in a solvent (e.g., water). The zinc source is selected from the group consisting of zinc sulfate hepta-hydrate (ZnSo ₄ .7H ₂ O), zinc sulfate (ZnSO ₄ ), zinc chloride (ZnCl ₂ ), zinc nitrate (Zn (NO ₃ ) ₂ ) (Zinc acetate dihydrate, (CH ₃ COO) ₂ Zn · 2H ₂ O).

In addition, the sulfur precursor solution can be formed by dissolving a sulfur source and ammonium hydroxide (NH ₄ OH) in a solvent (e.g., water). The source of sulfur may comprise at least one of thiourea (CH ₄ N ₂ S), sodium thiosulfate (Na ₂ S ₂ O ₃ ), sodium sulfide (Na ₂ S) and hydrogen sulfide (H ₂ S) .

Further, a solution containing hydroxide ions can be formed by dissolving at least any one solvent of the aqueous sodium hydroxide (NaOH), ammonium hydroxide (NH ₄ OH) and ammonium acetate _{(NH 4 CH 3 CO 2)} .

For example, a substrate is prepared by heating to about 100 ° C to 200 ° C, and a solution containing the hydroxide ion, the zinc precursor solution and the sulfur precursor solution are mixed in a micro reactor to prepare a mixture . A thin film can be formed by impinging the mixture on a heated substrate. At this time, the method of impinging the mixture on the substrate can continuously supply the mixture onto the substrate by using a spin coating method so that the mixture can be continuously formed on the substrate. Also, the Zn (O, S) film can be deposited by impinging the mixture on the heated substrate at a flow rate of about 50 ml / sec to 150 ml / sec for about 60 seconds to 180 seconds. Hereinafter, the method of spraying the mixture onto the substrate can be understood as a Continuos Flow Reactor (hereinafter referred to as CFR) -spin coating method. Finally, a Zn (O, S) thin film can be formed by heat-treating the Zn (O, S) film at a temperature ranging from about 150 ° C to 250 ° C in an atmospheric pressure atmosphere.

An exemplary reaction process for forming the Zn (O, S) thin film described above will be described below.

Zinc sulfate (ZnSO ₄ .7H ₂ O) and thiourea (CS (NH ₂ ) ₂ ) may each be a source material of zinc and sulfur. Ammonia solution (NH ₄ OH) and hydrazine hydrate _{(hydrazine hydrate, N 2 H 4} ) a CBD (Chemical Bath Deposition) to prevent the powder formed in the solution process and the composites to produce a zinc ion (Zn ²⁺⁾ (complexing agent ).

The ZnS thin film is formed on the substrate by the following reactions.

First, zinc ions (Zn ²⁺ ) are formed by the decomposition of ZnSO 4 salt according to equation (1).

Equation (1):

Sulfur ions (S ^2- ) are formed by the hydrolysis of thiourea as shown in equation ( ² ).

Equation (2):

In these solutions, ammonia reacts with zinc ions (Zn ²⁺ ) to form zinc ligands, and ammonia hydroxides form hydroxide ions (OH ^- ) to produce sulfur ions (S ^2- ) ).

Equation (3):

Equation (4):

Equation (5):

Next, a ZnS thin film is formed on the substrate surface by the formula (6).

Equation (6):

The presence of ZnO and / or Zn (OH ₂ ) impurities in the ZnS thin film can increase the efficiency of the solar cell. In the present invention, the Zn (O, S) thin film can be formed by a CFR-spin coating method including the following reactions.

As in equation (7), zinc hydroxide is produced in a solution containing hydroxide ions.

Equation (7):

The zinc oxide can be formed by drying during the heat treatment of the initially deposited film as shown in equation (8).

Equation (8):

The process of forming the Zn (O, S) thin film by the CBD process requires a long time of at least 1 hour, whereas when the solution proposed in the present invention and the CFR-spin coating method are used, , S) thin film can be completed in 5 minutes or less.

Hereinafter, experimental examples are provided to facilitate understanding of the present invention. It should be understood, however, that the following examples are for the purpose of promoting understanding of the present invention and are not intended to limit the scope of the present invention.

Soda lime glass (SLG) is used as a substrate. Sodium hydroxide, acetone, methanol and distilled water having a concentration of 1 M were sequentially sonicated for about 15 minutes each to remove residual dust and organic matter from the soda lime glass surface. Thereafter, the moisture of the surface of the soda lime glass washed with nitrogen gas (N ₂ ) was removed.

The temperature of the soda lime glass is fixed at about 110 캜, and the temperature of the water bath is fixed at about 90 캜. (ZnSO ₄ · 7H ₂ O), thiourea (CH ₄ N ₂ S) and ammonium acetate (NH ₄ CH ₃ CO ₂ ) in water (DI) Prepare the mixture by mixing the precursor solution in a micro reactor. The concentration of the zinc sulfate hepta-hydrate (ZnSO ₄ .7H ₂ O), the concentration of the thiourea (CH ₄ N ₂ S) and the concentration of the ammonium acetate (NH ₄ CH ₃ CO ₂ ) May be 0.05 M, 0.066 M and 0.012 M, respectively, in 100 mL of water.

Ammonium acetate is used as a complex agent. Liquid sodium hydroxide (NaOH) may be provided to control the pH. The mixing ratio of the precursor solution and the liquid sodium hydroxide may vary in terms of pH. The flow rate of the mixture in the microreactor was approximately 0.1 liter / min, the rotation speed of the spin coater on which the substrate was mounted was approximately 1500 rpm, and the time during which the mixture collides with the substrate was set to approximately 2 minutes.

The initially deposited Zn (O, S) film was annealed at a temperature of 200 ° C for about 30 minutes under atmospheric pressure to improve the crystallinity of the film formed by the above-described method and to remove residual pores, S) thin film is approximately 40 nm.

FIG. 1 is a graph illustrating the light transmittance of a Zn (O, S) thin film implemented in a manufacturing method according to an embodiment of the present invention. Referring to FIG. 1, it can be seen that the Zn (O, S) thin film formed by annealing at a temperature of 200 ° C. is more than 85% in the visible region.

FIG. 2 is a graph showing the XRD analysis results of the Zn (O, S) thin film implemented by the manufacturing method according to an embodiment of the present invention. Referring to FIG. 2, the crystal structure and crystal orientation of the Zn (O, S) thin film formed by annealing annealing at a temperature of 200 ° C. for 30 minutes are shown by a CFR-spin coating method. In the XRD spectrum, it can be confirmed that the peak of ZnS and the peak of ZnO are coupled.

The diffraction peaks detected at 2θ = 31.73 °, 34.46 °, 36.21 °, 47.47 °, 56.21 °, 62.75 °, and 67.85 ° in JCPDS 00-080-0074 are the (100), 9002 (101), (102), (110), (103) and (112) crystal planes respectively. On the other hand, the diffraction peaks detected at 2θ = 29.06 °, 49.40 ° and 57.42 ° correspond to the (111), (220) and (311) crystal planes of the cubic ZnS structure, respectively. These peaks are in good agreement with the database of JCPDS 01-079-0043. No peak corresponding to hexagonal type ZnS was detected in this experiment. ZnS exists in two types of crystal form. At relatively high annealing temperature, ZnS is formed in hexagonal crystal form. In relatively low temperature annealing condition, cubic crystal form ZnS is formed. In this experiment, the annealing process was performed at a relatively low temperature. Therefore, it was confirmed that the crystal form of ZnS formed was cubic crystal form rather than hexagonal form.

FIGS. 3A to 3C are graphs showing XPS analysis results of a Zn (O, S) thin film implemented by a manufacturing method according to an embodiment of the present invention.

Referring to FIG. 3A, a Zn 2p core level spectrum appears. The peak located at 1022.38 V corresponds to the binding energy corresponding to the Zn 2p _3/2 electron emitted from the zinc element and the peak located at 1045.48 V corresponds to the binding energy corresponding to the Zn 2p _1/2 electron emitted from the zinc element . Referring to FIG. 3B, an S 2p core level spectrum appears. The peak located at 162.38 V is due to the S 2p electron state released from the element. Referring to FIG. 3C, the peak located at 531.98 V corresponds to the O < 1s > electron state emitted from the element.

As described above, the manufacturing method of the Zn (O, S) thin film according to the present invention is performed at a relatively low temperature by using a modified Continuous Flow Reactor (hereinafter, referred to as CFR) -spin coating method of the CBD process The Cd-free buffer layer which is harmless to the human body can be manufactured at a low cost by shortening the deposition time.

In addition, the developed CFR-spin coating method can be applied to various fields such as semiconductor, optical, and energy. In addition to Zn (O, S) thin film, it is also possible to use a chalcogenide compound thin film solar cell and a transparent thin film transistor ) Can be applied to various applications.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (7)

Preparing a solution containing a zinc precursor solution, a sulfur precursor solution and a hydroxide ion, respectively;
Mixing the zinc precursor solution, the sulfur precursor solution and the solution containing hydroxide ions in a micro reactor to prepare a mixture;
Continuously supplying the mixture onto the substrate using a spin coating method so that the mixture can be continuously formed on the substrate, and impinging the mixture on the substrate to form a thin film; And
Heat treating the thin film;
, ≪ / RTI &
The annealing of the thin film was performed at a temperature of 200 ° C. The XRD spectrum of the thin film exhibited a peak of coupled ZnS and a peak of ZnO. The peak of ZnS was not a hexagonal ZnS structure, and a peak of the ZnO corresponds to a crystal plane of the hexagonal ZnO structure,
Zn (O, S) thin film. The method according to claim 1,
The zinc precursor solution may be selected from the group consisting of zinc sulfate hepta-hydrate (ZnSO ₄ .7H ₂ O), zinc sulfate (ZnSO ₄ ), zinc chloride (ZnCl ₂ ), zinc nitrate (Zn (NO ₃ ) ₂ ) Wherein the Zn (O, S) thin film is formed by dissolving at least one of zinc acetate dihydrate (CH ₃ COO) ₂ Zn · 2H ₂ O in a solvent. The method according to claim 1,
The sulfur precursor solution is prepared by dissolving at least one of thiourea (CH ₄ N ₂ S), sodium thiosulfate (Na ₂ S ₂ O ₃ ), sodium sulfide (Na ₂ S) and hydrogen sulfide (H ₂ S) (O, S) thin film formed on the substrate. The method according to claim 1,
A solution containing the hydroxide ion is ammonium hydroxide, sodium hydroxide (NaOH), (NH ₄ OH) and ammonium acetate (NH ₄ CH ₃ CO ₂₎ of at least one of dissolving in a solvent is formed, Zn (O, S) films ≪ / RTI > A precursor solution in which zinc sulfate hepta-hydrate (ZnSO ₄ .7H ₂ O), thiourea (CH ₄ N ₂ S) and ammonium acetate (NH ₄ CH ₃ CO ₂ ) Mixing in a micro reactor to prepare a mixture;
Continuously supplying the mixture onto the substrate using a spin coating method so that the mixture can be continuously formed on the substrate, and impinging the mixture on the substrate to form a thin film; And
Heat treating the thin film;
, ≪ / RTI &
The annealing of the thin film was performed at a temperature of 200 ° C. The XRD spectrum of the thin film exhibited a peak of coupled ZnS and a peak of ZnO. The peak of ZnS was not a hexagonal ZnS structure, and a peak of the ZnO corresponds to a crystal plane of the hexagonal ZnO structure,
Zn (O, S) thin film. 6. The method of claim 5,
The concentration of the zinc sulfate hepta-hydrate (ZnSO ₄ .7H ₂ O), the concentration of the thiourea (CH ₄ N ₂ S) and the concentration of the ammonium acetate (NH ₄ CH ₃ CO ₂ ) Were 0.05 M, 0.066 M and 0.012 M, respectively, in 100 ml of water,
Wherein the flow rate of the mixture in the microreactor is 0.1 liter / min, the rotation speed of the spin coater on which the substrate is mounted is 1500 rpm, and the time when the mixture collides with the substrate is approximately 2 minutes.
Zn (O, S) thin film. 6. The method of claim 5,
Wherein the step of heat treating the thin film comprises heat treating the thin film at 200 ° C under atmospheric pressure for 30 minutes.

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