KR101322681B1 - Czts thin film prepared by electrostatic spray and preparing method of the same - Google Patents

Abstract

A method of manufacturing a CZTS (Cu ₂ ZnSnS ₄ ) thin film, a CZTS thin film manufactured by the method, and a solar cell including the CZTS thin film.

Description

CZTS thin film manufactured by electrostatic spraying method and its manufacturing method {CZTS THIN FILM PREPARED BY ELECTROSTATIC SPRAY AND PREPARING METHOD OF THE SAME}

The present application relates to a method for producing a CZTS (Cu ₂ ZnSnS ₄ ) thin film, a CZTS thin film manufactured by the method, and a solar cell including the CZTS thin film.

Due to continued industrial development, fossil fuel depletion and greenhouse gas emissions continue to develop and research alternative energy sources such as solar, wind and tidal energy. Among them, solar energy has been continuously focused on research on solar cells because of the advantage that it can be obtained indefinitely.

Solar cells can be roughly divided into silicon-based, (inorganic) compound-based, and other solar cells. Among these, research on silicon-based solar cells is most actively performed. Silicon-based solar cells can be classified into monocrystalline, polycrystalline, amorphous, and thin film types. Monocrystalline and polycrystalline silicon solar cells account for more than 88% of the world production, and amorphous solar cells account for about 5%. However, the silicon-based solar cell has the highest efficiency of the single crystal silicon solar cell, but has a disadvantage in that the unit cost is relatively high due to the complicated process involved in manufacturing single crystal silicon.

Compound-based solar cells are composed of inorganic materials and may be classified into group I-III-IV, group II-VI, and group III-V compound semiconductor solar cells. Among them, the I-III-VI compound solar cell is a chalcogenide compound semiconductor represented by CuInSe _2, and has a direct transition energy bandgap structure and has a light absorption coefficient of 10 ⁵ cm ⁻¹ . Among the highest and 1 to 2 ㎛ thickness of the solar cell can be produced with high efficiency, it suggested the possibility of improving the economics by replacing the crystalline silicon solar cell.

However, CuInSe ₂ has been studied to achieve a bandgap of 1.04 eV, which is an ideal value of about 1.5 eV. One of them replaces a part of In with Ga and a part or all of Se with S to replace CIGSS (Cu (In _x Ga _{1 -x} ) (Se _y S _{1 -y} ) ₂ ) or CIGS (Cu (In _x Ga _{1 -x} ) S ₂ ) is prepared. However, although Se-based compounds such as CIGSS exhibit high conversion efficiency of the manufactured thin film, Ga or In has a disadvantage of low reserves in the crust, and especially in the case of In, the In-tin oxide thin film mainly used in the display field is used. As the demand for the indium tin oxide is increased, there is a possibility of causing a raw material problem in manufacturing a solar cell thin film.

Therefore, in order to solve the above problems and lower the manufacturing cost of the solar cell thin film, CZTS (Cu ₂ ZnSnS ₄ ), a four-component compound using Zn, Sn, and S, which is rich in crust, has been proposed as an alternative. The CZTS has attracted attention because it can be replaced with a low cost element while maintaining high light absorption coefficient and band gap energy, which are advantages of existing CIGS-based solar cell thin films.

In the CZTS thin film manufacturing method, a thin film was conventionally synthesized by a method such as thermal evaporation, co-evaporation, sputtering, or electron beam evaporation. The method required complicated equipment and increased production costs as the reaction was carried out in a high temperature and / or vacuum atmosphere.

Therefore, a study was conducted to synthesize CZTS thin films in a non-vacuum atmosphere such as electrochemical deposition and ultrasonic spray deposition. For example, there have been related studies such as "Method for producing CZTS thin film using single process electrodeposition (Korean Patent No. 10-1093663)". However, this method has a limitation in that the surface of the obtained thin film is not uniform and the shape of grain is not constant.

The present application provides a method for producing a CZTS thin film, which is economically and structurally improved by electrostatic spraying in a non-vacuum state, a CZTS thin film manufactured by the method, and a solar cell including the CZTS thin film.

However, the problem to be solved by the present application is not limited to the above-mentioned problem, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

A first aspect of the present disclosure includes preparing a precursor solution comprising a copper source, a zinc source, a tin source, and a sulfur source; Depositing a thin film by electrospraying the precursor solution on a substrate in a non-vacuum state; And it may provide a method for producing a CZTS (Cu ₂ ZnSnS ₄ ) thin film comprising the step of annealing the thin film.

According to one embodiment of the present application, each of the copper source, the zinc source, and the tin source may be one each including hydrochloride or nitrate, but is not limited thereto.

According to an embodiment of the present disclosure, the copper source is copper chloride (CuCl ₂ ), the zinc source is zinc chloride (ZnCl ₂ ), the tin source is tin chloride (SnCl ₂ ), and the sulfur source is thiourea (( NH ₂ ) ₂ CS) may be included, but is not limited thereto.

According to an embodiment of the present disclosure, the concentration of the copper chloride, the zinc chloride, the tin chloride, and the thiourea may be about 0.01 M to about 0.2 M, about 0.005 M to about 0.1 M, and about 0.005 M to about 0.1, respectively. M, and from about 0.04 M to about 0.8 M, but is not limited thereto.

According to one embodiment of the present application, the precursor solution may include, but is not limited to, the copper source, the zinc source, the tin source, and the sulfur source dispersed, dissolved, or dispersed and dissolved in a polar solvent. It doesn't happen.

According to one embodiment of the present application, the polar solvent may include water, ethanol, or a mixture of water and ethanol, but is not limited thereto.

According to one embodiment of the present application, the mixture of water and ethanol may include, but is not limited to, the water and the ethanol in a ratio of about 7 to about 3.

According to one embodiment of the present application, the substrate may include glass or soda lime glass, but is not limited thereto.

According to one embodiment of the present application, the electrostatic spraying may include, but is not limited to, electrospraying the precursor solution on the substrate at a rate of about 0.001 ml / min to about 0.02 ml / min.

According to one embodiment of the present application, the electrostatic spray may include, but is not limited to being carried out while applying a DC high voltage of about 1 kV to about 10 kV to the precursor solution.

According to one embodiment of the present application, the electrostatic spray may include, but is not limited to, electrospraying the precursor solution for about 30 minutes to about 2 hours.

According to the exemplary embodiment of the present disclosure, the depositing of the thin film may include maintaining the temperature of the substrate at about 100 ° C. to about 300 ° C., but is not limited thereto.

According to an embodiment of the present disclosure, the annealing of the thin film may include, but is not limited to being performed at a temperature of about 250 ℃ to about 500 ℃.

According to one embodiment of the present application, annealing the thin film may include performing about 30 minutes to about 2 hours, but is not limited thereto.

The second aspect of the present application provides a CZTS thin film manufactured by the manufacturing method of the first aspect of the present application.

A third aspect of the present application provides a solar cell comprising a CZTS thin film according to the second aspect of the present application.

According to the present application, by manufacturing the CZTS thin film by the electrostatic spray method, it is possible to solve the problems caused by the composition of the high temperature and / or vacuum atmosphere, and the complicated equipment required when manufacturing the CZTS thin film by conventional thermal evaporation. In addition, when the CZTS thin film is manufactured by conventional electrochemical deposition or the like, the problem that the surface of the thin film is non-uniform and the shape of grain is not fixed may be solved.

In addition, according to the present application by depositing the CZTS thin film by the electrostatic spray method and performing the annealing process, the structure of the CZTS thin film is uniform, and the band gap is similar to the thin film produced by the vacuum process to achieve the effect of lowering the unit cost can do.

The CZTS thin film prepared according to the present invention is deposited in a non-vacuum atmosphere, so there is no need for complicated equipment and the manufacturing cost is low, and the surface of the thin film has a uniform grain shape.

1 is a flow chart showing a method of manufacturing a CZTS thin film according to an embodiment of the present application.
Figure 2 is a schematic diagram of the electrostatic spraying apparatus used in the manufacture of the CZTS thin film according to an embodiment of the present application.
3 is an X-ray diffraction spectrum of a CZTS thin film deposited by an electrospray method according to an embodiment of the present disclosure.
4 is an X-ray diffraction spectrum of a CZTS thin film deposited by an electrospray method according to an embodiment of the present disclosure.
5 is an AFM (Atomic Force Microscope) photograph of a CZTS thin film deposited by an electrospray method according to an embodiment of the present application.
6 is a scanning electron microscope (SEM) photograph of the CZTS thin film surface deposited by the electrospray method according to an embodiment of the present application.
7 is a graph showing the bandgap energy of the CZTS thin film deposited by the electrostatic spray method according to an embodiment of the present application.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. It should be understood, however, that the present invention may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, the same reference numbers are used throughout the specification to refer to the same or like parts.

Throughout this specification, when an element is referred to as "including " an element, it is understood that the element may include other elements as well, without departing from the other elements unless specifically stated otherwise.

The terms "about "," substantially ", etc. used to the extent that they are used herein are intended to be taken as a reference to either the numerical value or to the numerical value when the manufacturing and material tolerance inherent in the stated meaning is presented, Accurate or absolute numbers are used to prevent unauthorized exploitation by unauthorized intruders of the mentioned disclosure. Also, throughout the present specification, the phrase " step "or" step "does not mean" step for.

Throughout this specification, when a member is " on " another member, it includes not only when the member is in contact with the other member, but also when there is another member between the two members.

Throughout this specification, the term " combination thereof " included in the expression of the machine form means one or more combinations or combinations selected from the group consisting of the constituents described in the expression of the machine form, And the like.

Throughout this specification, the description of "A and / or B" means "A, B, or A and B".

A first aspect of the present disclosure includes preparing a precursor solution comprising a copper source, a zinc source, a tin source, and a sulfur source; Depositing a thin film by electrospraying the precursor solution on a substrate in a non-vacuum state; And it may provide a method for producing a CZTS (Cu ₂ ZnSnS ₄ ) thin film comprising the step of annealing the thin film.

1 is a flow chart showing a method of manufacturing a CZTS thin film according to an embodiment of the present application.

First, a precursor solution including a copper source, a zinc source, a tin source, and a sulfur source is prepared (S110). For example, the molar concentration of copper in the precursor solution is about 0.01 M to 0.2 M, about 0.01 M to about 0.17 M, about 0.01 M to about 0.14 M, about 0.01 M to about 0.11 M, about 0.01 M to about 0.08 M, about 0.01 M to about 0.05 M, or about 0.01 M to about 0.02 M, about 0.02 M to about 0.2 M, about 0.04 M to about 0.2 M, about 0.06 M to about 0.2 M, about 0.09 M to about 0.2 M , About 0.12 M to about 0.2 M, about 0.15 M to about 0.2 M, or about 0.18 M to about 0.2 M, but is not limited thereto. For example, the molar concentration of zinc in the precursor solution is about 0.005 M to about 0.1 M, about 0.005 M to about 0.08 M, about 0.005 M to about 0.06 M, about 0.005 M to about 0.04 M, about 0.005 M to about 0.02 M, about 0.005 M to about 0.01 M, about 0.005 M to about 0.008 M, about 0.008 M to about 0.1 M, about 0.01 M to about 0.1 M, about 0.03 M to about 0.1 M, about 0.05 M to about 0.1 M , About 0.07 M to about 0.1 M, or about 0.09 M to about 0.1 M, but is not limited thereto. For example, the molar concentration of tin in the precursor solution is about 0.005 M to about 0.1 M, about 0.005 M to about 0.08 M, about 0.005 M to about 0.06 M, about 0.005 M to about 0.04 M, about 0.005 M to about 0.02 M, about 0.005 M to about 0.01 M, about 0.005 M to about 0.008 M, about 0.008 M to about 0.1 M, about 0.01 M to about 0.1 M, about 0.03 M to about 0.1 M, about 0.05 M to about 0.1 M , About 0.07 M to about 0.1 M, or about 0.09 M to about 0.1 M, but is not limited thereto. For example, the molar concentration of sulfur in the precursor solution is about 0.04 M to about 0.8 M, about 0.06 M to about 0.8 M, about 0.08 M to about 0.8 M, about 0.1 M to about 0.8 M, about 0.2 M to about 0.8 M, about 0.3 M to about 0.8 M, about 0.4 M to about 0.8 M, about 0.5 M to about 0.8 M, about 0.6 M to about 0.8 M, about 0.7 M to about 0.8 M, about 0.04 M to about 0.7 M, About 0.04 M to about 0.6 M, about 0.04 M to about 0.5 M, about 0.04 M to about 0.4 M, about 0.04 M to about 0.3 M, about 0.04 M to about 0.2 M, about 0.04 M to about 0.1 M, about 0.04 M to about 0.08 M, or about 0.04 M to about 0.06 M, but is not limited thereto.

According to the exemplary embodiment of the present application, the copper source, the zinc source, or the tin source may be each one including hydrochloride or nitrate, but is not limited thereto.

According to an embodiment of the present disclosure, the copper source is copper chloride (CuCl ₂ ), the zinc source is zinc chloride (ZnCl ₂ ), the tin source is tin chloride (SnCl ₂ ), and the sulfur source is thiourea (( NH ₂ ) ₂ CS) may be included, but is not limited thereto.

For example, the molar concentration of copper chloride is about 0.01 M to 0.2 M, about 0.01 M to about 0.17 M, about 0.01 M to about 0.14 M, about 0.01 M to about 0.11 M, about 0.01 M to about 0.08 M, About 0.01 M to about 0.05 M, or about 0.01 M to about 0.02 M, about 0.02 M to about 0.2 M, about 0.04 M to about 0.2 M, about 0.06 M to about 0.2 M, about 0.09 M to about 0.2 M, about 0.12 M to about 0.2 M, about 0.15 M to about 0.2 M, or about 0.18 M to about 0.2 M, but is not limited thereto. For example, the molar concentration of zinc chloride is about 0.005 M to about 0.1 M, about 0.005 M to about 0.08 M, about 0.005 M to about 0.06 M, about 0.005 M to about 0.04 M, about 0.005 M to about 0.02 M , About 0.005 M to about 0.01 M, about 0.005 M to about 0.008 M, about 0.008 M to about 0.1 M, about 0.01 M to about 0.1 M, about 0.03 M to about 0.1 M, about 0.05 M to about 0.1 M, about 0.07 M to about 0.1 M, or about 0.09 M to about 0.1 M, but is not limited thereto. For example, the molar concentration of tin chloride is about 0.005 M to about 0.1 M, about 0.005 M to about 0.08 M, about 0.005 M to about 0.06 M, about 0.005 M to about 0.04 M, about 0.005 M to about 0.02 M , About 0.005 M to about 0.01 M, about 0.005 M to about 0.008 M, about 0.008 M to about 0.1 M, about 0.01 M to about 0.1 M, about 0.03 M to about 0.1 M, about 0.05 M to about 0.1 M, about 0.07 M to about 0.1 M, or about 0.09 M to about 0.1 M, but is not limited thereto. For example, the molar concentration of the thiourea is about 0.04 M to about 0.8 M, about 0.06 M to about 0.8 M, about 0.08 M to about 0.8 M, about 0.1 M to about 0.8 M, about 0.2 M to about 0.8 M , About 0.3 M to about 0.8 M, about 0.4 M to about 0.8 M, about 0.5 M to about 0.8 M, about 0.6 M to about 0.8 M, about 0.7 M to about 0.8 M, about 0.04 M to about 0.7 M, about 0.04 M to about 0.6 M, about 0.04 M to about 0.5 M, about 0.04 M to about 0.4 M, about 0.04 M to about 0.3 M, about 0.04 M to about 0.2 M, about 0.04 M to about 0.1 M, about 0.04 M To about 0.08 M, or about 0.04 M to about 0.06 M, but is not limited thereto.

According to the exemplary embodiment of the present application, the precursor solution may include one in which the copper source, the zinc source, the tin source, and the sulfur source are dispersed, dissolved, or dispersed and dissolved in a polar solvent. It is not limited.

According to one embodiment of the present application, the polar solvent may include water, ethanol, or a mixture of water and ethanol, but is not limited thereto. For example, the polar solvent has a ratio of water and ethanol (volume ratio) of about 0 to about 10, about 1 to about 9, about 2 to about 8, about 3 to about 7, about 4 to about 6, and about 5 About 5, about 6 to about 4, about 7 to about 3, about 8 to about 2, about 9 to about 1, or about 10 to about 0, but is not limited thereto.

Subsequently, the precursor solution is electrosprayed onto the substrate in a non-vacuum state to deposit a thin film (S130). For example, the electrostatic spraying step may include depositing a thin film on a substrate by generating droplets through electrospraying using the precursor solution using an electrostatic spraying device, but is not limited thereto.

In this regard, Figure 2 is a schematic diagram of the electrostatic spray device used in one embodiment of the present application. The electrostatic spraying device may include a syringe pump, a stainless needle, a substrate, and a high voltage applying device, but is not limited thereto. For example, the electrostatic spraying device supplies the precursor solution to the stainless steel needle at a constant flow rate using the syringe pump, and at this time, a stainless needle having a direct current high voltage formed on the substrate and droplets using the high voltage applying device. In addition to this, the shape of the droplets may include a cone-jet mode, but may include, but is not limited thereto. For example, the distance between the substrate and the tip of the stainless steel needle may range from about 1 cm to about 10 cm, about 2 cm to about 10 cm, about 3 cm to about 10 cm, about 4 cm to about 10 cm, and about 5 cm to About 10 cm, about 6 cm to about 10 cm, about 7 cm to about 10 cm, about 8 cm to about 10 cm, about 9 cm to about 10 cm, about 1 cm to about 9 cm, about 1 cm to about 8 cm, about 1 cm to about 7 cm, about 1 cm to about 6 cm, about 1 cm to about 5 cm, about 1 cm to about 4 cm, about 2 cm to about 4 cm, about 3 cm to about 4 cm, About 1 cm to about 3 cm, or about 1 cm to about 2 cm, but is not limited thereto.

According to one embodiment of the present application, the substrate may include glass or soda lime glass, but is not limited thereto. For example, the substrate may include, but is not limited to, washing with isopropyl alcohol and / or distilled water. For example, the substrate may include silica, and may be coated with molybdenum, but is not limited thereto.

According to one embodiment of the present application, the electrostatic spray may be, but is not limited to electrostatic spraying the precursor solution on the substrate at a rate of about 0.001 ml / min to about 0.02 ml / min. For example, the electrostatic spraying may cause the precursor solution to contain from about 0.001 ml / min to about 0.02 ml / min, from about 0.001 ml / min to about 0.01 ml / min, from about 0.001 ml / min to about 0.007 ml / min, about 0.001 ml / min to about 0.005, about 0.001 ml / min to about 0.003 ml / min, about 0.003 ml / min to about 0.02 ml / min, about 0.005 ml / min to about 0.02 ml / min, about 0.008 ml / min to about Electrostatic spraying on the substrate at a rate of 0.02 ml / min, about 0.01 ml / min to about 0.02 ml / min or about 0.015 ml / min to about 0.02 ml / min, but is not limited thereto.

For example, the electrostatic spraying is about 10 minutes to about 3 hours, about 10 minutes to about 2 hours, about 10 minutes to about 1 hour 30 minutes, about 10 minutes to about 1 hour, about 20 minutes to about 3 hours, About 20 minutes to about 2 hours, about 20 minutes to about 1 hour 30 minutes, about 20 minutes to about 1 hour, about 30 minutes to about 3 hours, about 30 minutes to about 2 hours, about 30 minutes to about 1 hour 30 Minutes, about 30 minutes to about 1 hour, about 45 minutes to about 3 hours, about 45 minutes to about 2 hours, about 45 minutes to about 1 hour 30 minutes, about 45 minutes to about 1 hour, about 1 hour to about 3 Electrostatic spraying for a time, about 1 hour to about 2 hours, or about 1 hour to about 1 hour 30 minutes, but is not limited thereto.

According to one embodiment of the present application, the electrostatic spraying may include electrostatic spraying by applying a DC high voltage of about 1 kV to about 10 kV to the precursor solution, but is not limited thereto. For example, the electrostatic spray is applied in the precursor solution about 1 kV to about 8 kV, about 1 kV to about 6 kV, about 1 kV to about 4 kV, about 1 kV to about 2 kV, about 2 kV to about 10 kV, about 4 kV to about 10 kV, about 6 kV to about 10 kV, or about 8 kV to about 10 kV DC high voltage may be applied to electrostatic spraying, but is not limited thereto.

According to the exemplary embodiment of the present disclosure, the depositing of the thin film may include maintaining the temperature of the substrate at about 100 ° C. to about 300 ° C., but is not limited thereto. For example, the temperature of the substrate is about 100 ℃ to about 300 ℃, about 120 ℃ to about 300 ℃, about 140 ℃ to about 300 ℃, about 160 ℃ to about 300 ℃, about 180 ℃ to about 300 ℃, about 200 ° C to about 300 ° C, about 200 ° C to about 280 ° C, about 200 ° C to about 260 ° C, about 200 ° C to about 240 ° C, about 200 ° C to about 220 ° C, about 220 ° C to about 300 ° C, about 240 ° C To about 300 ° C, about 260 ° C to about 300 ° C, or about 280 ° C to about 300 ° C, but is not limited thereto.

Next, the thin film is annealed (S150). For example, the annealing may include, but is not limited to, improving the structural and / or electrical properties of the thin film. For example, the annealing includes but is not limited to being performed using a reduction furnace.

For example, the annealing may take about 30 minutes to about 3 hours, about 30 minutes to about 2 hours 30 minutes, about 30 minutes to about 2 hours, about 30 minutes to about 1 hour 30 minutes, about 30 minutes to about 1 hour. , About 1 hour to about 3 hours, about 1 hour 30 minutes to about 3 hours, about 2 hours to about 3 hours, or about 2 hours 30 minutes to about 3 hours.

For example, the annealing may include about 0.5 atm to about 5 atm, about 1 atm to about 5 atm, about 2 atm to about 5 atm, about 3 atm to about 5 atm, about 4 atm to about 5 atm, and about 0.5 atm. To about 4 atmospheres, about 0.5 atmospheres to about 3 atmospheres, about 0.5 atmospheres to about 2 atmospheres, or about 0.5 atmospheres to about 1 atmospheres, but is not limited thereto.

According to an embodiment of the present disclosure, the annealing may be performed at a temperature of about 250 ° C. to about 500 ° C., but is not limited thereto. For example, the annealing may be about 250 ° C. to about 450 ° C., about 250 ° C. to about 400 ° C., about 250 ° C. to about 350 ° C., about 250 ° C. to about 300 ° C., about 300 ° C. to about 500 ° C., about 350 ° C. To about 500 ° C., about 400 ° C. to about 500 ° C., or about 450 ° C. to about 500 ° C., but is not limited thereto.

A second aspect of the present disclosure can provide a CZTS thin film having improved structural, crystalline, and optical properties. The CZTS thin film may be used as a substitute material of the solar cell by replacing the existing CIGSS and CIGS thin film, but is not limited thereto. For example, the CZTS thin film may be manufactured at a lower cost than the CZTS thin film manufactured by a conventional manufacturing method, and thus may include economics, but is not limited thereto. For example, the CZTS thin film may include improved structural or optical properties such as surface structure or grain shape compared to the CZTS thin film manufactured by the conventional method of manufacturing a CZTS thin film in a non-vacuum state. It is not limited. For example, the CZTS thin film may be a CZTS thin film manufactured by the method according to the first aspect of the present application, but is not limited thereto.

The third aspect of the present application can provide a solar cell including a CZTS thin film according to the second aspect of the present application. For example, the CZTS thin film may be used as the light absorption layer of the solar cell, but is not limited thereto.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the following examples are for illustrative purposes only and are not intended to limit the scope of the present invention.

[ Example ]

Example 1

In this embodiment, the precursor solution is a mixture of water and ethanol as a solvent of a precursor material containing CuCl ₂ 0.02 M, ZnCl ₂ 0.01 M, SnCl ₂ 0.01 M, (NH ₂ ) ₂ CS 0.08 M (water: ethanol = 7: 3) were mixed in order and the solvent was prepared by dispersing and / or dissolving the precursor material using a stirrer for about 1 hour. Thereafter, the precursor solution was added to the electrostatic spraying device, the flow rate of the syringe pump was maintained at 0.002 ml / min, and electrostatic spraying was performed on a glass substrate at 250 ° C. for 1 hour. At this time, the distance between the needle tip of the electrostatic spray device and the lower glass substrate was maintained to 4 cm, and a high voltage of 5 kV was applied between the needle and the lower substrate through a high voltage application device to prepare a CZTS thin film.

[Example 2]

In the present embodiment, the CZTS thin film was manufactured by the same method as Example 1 except that the CZTS thin film obtained by performing the electrospray process was additionally subjected to an annealing step at 290 ° C. for 1 hour in a reduction furnace.

[Example 3]

In this example, a CZTS thin film was manufactured in the same manner as in Example 2, except that the annealing was performed at 340 ° C.

Example 4

In this example, a CZTS thin film was manufactured in the same manner as in Example 2, except that the annealing was performed at 390 ° C.

[Example 5]

In this embodiment, a CZTS thin film was manufactured in the same manner as in Example 2, except that the annealing was performed at 440 ° C.

[Example 6]

In this embodiment, a CZTS thin film was manufactured in the same manner as in Example 1, except that the electrostatic spraying process of the precursor solution was performed for only 30 minutes.

[Example 7]

In this embodiment, a CZTS thin film was manufactured in the same manner as in Example 2, except that the electrostatic spraying process of the precursor solution was performed for only 30 minutes.

[Example 8]

In the present embodiment, a CZTS thin film was manufactured in the same manner as in Example 3, except that the electrostatic spraying process of the precursor solution was performed for only 30 minutes.

[Example 9]

In the present embodiment, a CZTS thin film was manufactured in the same manner as in Example 4, except that the electrostatic spraying process of the precursor solution was performed for only 30 minutes.

[Example 10]

In this embodiment, a CZTS thin film was manufactured in the same manner as in Example 5, except that the electrostatic spraying process of the precursor solution was performed for only 30 minutes.

[ Experimental Example ]

[Experimental Example 1]

X-ray diffraction spectrum analysis

In this Experimental Example, the CZTS thin films obtained in Examples 1 to 10 were analyzed by an X-ray diffractometer (XRD; X-ray Diffractometer) to confirm the crystal characteristics of the CZTS thin films. 4 is shown.

3 is an XRD spectrum of the CZTS thin film by the electrospray method obtained in Examples 1 to 5, in which the precursor solution is sprayed for 1 hour using an electrospray device and annealed at various temperatures. The obtained thin film exhibited (112), (200), (105), (220) and (312) crystal phases of Cu ₂ ZnSnS ₄ phase. Among them, the (112) phase was the most preferred crystal phase, and it was confirmed that the intensity of the X-ray diffraction spectrum of the deposited thin film increased with increasing temperature for performing the annealing process. However, it was observed that the thin film annealed at 440 ° C. had abnormalities such as Zn _{1 - x} S _x , Cu _{1 - x} S _x, etc. which appeared as a secondary phase in addition to the CZTS phase.

4 is an XRD spectrum of the CZTS thin film by the electrospray method obtained in Examples 6 to 10, in which the precursor solution was sprayed for 30 minutes using an electrospray device and annealed at various temperatures. Only the (112) crystal phase of the Cu ₂ ZnSnS ₄ phase was observed in the obtained thin film, and only the peak of a large region of the glass (silica) used as the substrate was observed on the X-ray diffraction spectrum. Accordingly, it can be seen from the results of FIGS. 3 and 4 that the deposition should be performed for at least 30 minutes in synthesizing the CZTS thin film using the electrostatic spray method.

[Experimental Example 2]

Atomic Force Microscopy (AFM) Analysis

In the present experimental example, to analyze the surface structure of the deposited CZTS thin film, the CZTS thin films obtained in Examples 1 to 5 were analyzed by an atomic force microscope (AFM), and the results are shown in FIG. 5. It was. 5 shows the surface of the CZTS thin film obtained by Example 1 (FIG. 5A), Example 2 (FIG. 5B), Example 3 (FIG. 5C), Example 4 (FIG. 5D) and Example 5 (FIG. 5E). The results of observing the roughness in the area of 5 μm × 5 μm using AFM are shown.

The results of the AFM analysis of FIG. 5 confirm that the grains forming the surface form aggregates by the annealing step, and thus, the shape of the surface becomes more uniform.

[Experimental Example 3]

Scanning Electron Microscopy (SEM)

In the present experimental example, to analyze the surface structure of the deposited CZTS thin film, the CZTS thin films obtained in Examples 1 and 4 were analyzed by Scanning Electron Microscope (SEM), and the results are shown in FIG. 6. 6-a is the thin film obtained in Example 1, and FIG. 6-b is the surface structure of the thin film obtained in Example 4. FIG. As shown in FIG. 6, it can be confirmed that the grains constituting the thin film are agglomerated by the heat treatment effect by performing the annealing step. The size of each grain forming the CZTS thin film by annealing was found to be several hundred nm to several μm, and the CZTS thin film was found to be denser through the annealing process.

[Experimental Example 4]

Optical characterization

In this Experimental Example, in order to confirm the optical characteristics of the CZTS thin film, the CZTS thin films obtained in Examples 1 and 4 were analyzed using a UV-vis spectrometer, and the bandgap of the thin film was analyzed. Energy is shown in FIG. 7.

The bandgap energy of the CZTS thin film obtained in Example 1 was about 1.76 eV, whereas the bandgap energy of the CZTS thin film of Example 4 obtained by performing an annealing process at 390 ° C. for 1 hour was about 1.55 eV.

From the optical property analysis, it was confirmed that the optical properties of the CZTS thin film obtained by performing the annealing process were improved.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments and the exemplary embodiments, and various changes and modifications may be made without departing from the scope of the present invention. It is evident that many variations are possible by those skilled in the art.

Claims (13)

Preparing a precursor solution comprising a copper source, a zinc source, a tin source, and a sulfur source;
Depositing a thin film by electrospraying the precursor solution on a substrate in a non-vacuum state; And
Annealing the thin film
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Method for producing a CZTS (Cu ₂ ZnSnS ₄ ) thin film.
The method of claim 1,
Wherein each of said copper source, said zinc source, and said tin source comprises hydrochloride or nitrate.
The method of claim 1,
The copper source is copper chloride (CuCl ₂ ), the zinc source is zinc chloride (ZnCl ₂ ), the tin source is tin chloride (SnCl ₂ ), and the sulfur source is thiourea ((NH ₂ ) ₂ CS), respectively. It will contain, CZTS thin film manufacturing method.
The method of claim 3, wherein
The concentration of the copper chloride, the zinc chloride, the tin chloride, and the thiourea is 0.01 M to 0.2 M, 0.005 M to 0.1 M, 0.005 M to 0.1 M, and 0.04 M to 0.8 M, respectively, CZTS thin film Manufacturing method.
The method of claim 1,
Wherein the precursor solution comprises the copper source, the zinc source, the tin source, and the sulfur source dispersed, dissolved, or dispersed and dissolved in a polar solvent.
The method of claim 5, wherein
The polar solvent comprises water, ethanol, or a mixture of water and ethanol, the method of producing a CZTS thin film.
The method of claim 1,
The annealing the thin film is carried out at a temperature of 250 ℃ to 500 ℃, CZTS thin film manufacturing method.
The method of claim 1,
The substrate comprises a glass or soda lime glass, the method of producing a CZTS thin film.
The method of claim 1,
The electrostatic spray is a method of producing a CZTS thin film, the precursor solution is electrostatic sprayed on the substrate at a rate of 0.001 ml / min to 0.02 ml / min.
The method of claim 1,
The electrostatic spraying is performed in a state where a direct current high voltage of 1 kV to 10 kV is applied to the precursor solution, CZTS thin film manufacturing method.
The method of claim 1,
The depositing the thin film includes maintaining the temperature of the substrate at 200 ° C to 300 ° C.
CZTS thin film prepared by the method according to any one of claims 1 to 11.
The solar cell comprising the CZTS thin film according to claim 12.

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