KR20110076754A - Method of fabricating cigs based nano particle - Google Patents

Abstract

PURPOSE: A method for manufacturing copper-indium-gallium-selenide-based nano particles is provided to reduce time required for manufacturing the nano particles using a colloidal method which mixes a pyridine solution and a methanol solution to synthesize the nano particles. CONSTITUTION: A pyridine solution is prepared by mixing an iodine compound of powder type CuI, InI_3, and GaI_3, and a pyridine solvent through a heating process at temperature between 40 and 80 degrees Celsius. Na_2Se is mixed with a methanol solvent to prepare a methanol solution. The pyridine solution and the methanol solution are prepared at inert atmosphere. The pyridine solution and the methanol solution are mixed to synthesize nano particles in an ice bath. NaI, which is generated as a byproduct, is eliminated.

Description

Method for fabricating CISS-based nanoparticles {Method of fabricating CIGS based nano particle}

The present invention relates to a method for producing CIGS nanoparticles, and more particularly, to a method for producing CIGS nanoparticles, which are mainly used as an absorbing layer of a solar cell, by a low temperature colloidal method.

A solar cell using a semiconductor is absorbed by a semiconductor while moving in the semiconductor when light is incident on the solar cell to generate electrons and hole pairs, and these pairs are separated by an internal electric field formed in the space charge region and collected at both ends of the electrode. In this case, when an external circuit is connected to the electrode, the photocurrent flows. Solar cells are classified into Si semiconductors or compound semiconductor solar cells according to their materials. Si semiconductors have been widely studied to date.

Si semiconductor is an indirect transition type semiconductor, and its light absorption coefficient cannot absorb photons more effectively than a direct transition type semiconductor, and thus requires a wider space charge region than the direct transition type. In addition, high purity Si is essential in order to prevent the recombination of electrons and holes generated in the space charge region by prolonging the life time of the carrier. need. Solar cells using high-purity single crystal Si have high efficiency but high manufacturing cost. Therefore, low efficiency polycrystalline Si or amorphous Si (amorphous-Si) is used to reduce the manufacturing cost, but it is not high in photoelectric conversion efficiency. Deterioration occurs when used for a long time.

Recently, solar cells using compound semiconductors have been researched and developed to compensate for the disadvantages of Si-based solar cells. Among the compound semiconductors, Cu (In _1-x Ga _x ) (Se _y S _1-y ) (CIGS), a group I-III-VI compound semiconductor belonging to the thin-film ternary compound, has a direct transition energy band gap of 1 eV or more. Not only does it have a high light absorption coefficient ( ¹ × 10 ⁵ cm ⁻¹ ), it is also known to be very electro-optically stable and to recover quickly from deterioration which degrades efficiency.

 However, co-evaporation, sputtering, chemical bath deposition (CBD), selenization, Various physicochemical thin film manufacturing methods such as spray pyrolysis have been tried, and an expensive vacuum device should be used to obtain high photoelectric conversion efficiency. It is also pointed out that it is very difficult to control the stoichiometric ratio by chemical bonding. In order to realize low cost of solar cells, it is necessary to develop a technology for manufacturing a light absorption layer by a method that does not use the existing high-cost and high-vacuum process.

 As a typical low-cost I-III-VI solar cell manufacturing process that does not use the above-mentioned vacuum process, we can consider the powder coating method by the manufacture of fine particles. Particle size should be preceded by a technique for synthesizing nano-sized particles. There are a number of methods for synthesizing nanoparticles at low temperatures, and recently, the solvent thermal method for synthesizing at a relatively high temperature is typical.

Solvent thermal method has the advantage of being able to synthesize particles at low cost in a simple process at low pressure, and easy to control the stoichiometric ratio. However, solvothermal method uses a strong basic toxic amine compound as a solvent, it is difficult to seal the reaction vessel and react for about 20 to 60 hours for a long time. Accordingly, there is a disadvantage that it is difficult to obtain the result designed before the reaction.

Therefore, the problem to be solved by the present invention is to provide a method for producing CIGS-based nanoparticles of low-cost CIGS nanoparticles to obtain a stable physical properties and to maximize the use time of toxic materials at a relatively low temperature without using a vacuum process .

In order to achieve the problem to be solved the CIGS-based nanoparticles to prepare a pyridine solution in which a mixture of iodine compounds of CuI, InI ₃ and GaI _{3 in} the form of a powder with a pyridine solvent, Na ₂ Se is methanol (methanol) Prepare a methanol solution mixed with a solvent. The pyridine solution and the methanol solution are then mixed to synthesize nanoparticles, followed by removal of byproduct NaI.

In the preparation method, the pyridine solution may be formed by heating to 40 ~ 80 ℃, the pyridine solution and the methanol solution may be formed in an inert atmosphere. In addition, the synthesis of the nanoparticles by mixing the pyridine solution and the methanol solution is preferably carried out in an ice bath.

According to the method for producing CIGS-based nanoparticles according to the present invention, by using a colloidal method of synthesizing nanoparticles by mixing a pyridine solution and a methanol solution, the nanoparticles can be obtained within a relatively short time, and the synthesis process is Since the process is performed at low temperatures, manufacturing costs can be reduced. In addition, inexpensive nanoparticles can be produced by a simple manufacturing process in an inert atmosphere of low vacuum, thereby making it possible to produce a low-cost and large-scale solar cell.

1 is a process block diagram showing a process of synthesizing CIGS-based nanoparticles according to the present invention.
Figure 2a is a graph of the composition ratio after the heat treatment in Ar atmosphere for 30 minutes at 400 ℃ after coating the CIGS nanoparticles synthesized by the present invention on a soda lime glass plate on which molybdenum (Mo) is deposited, and analyzed by EDX 2b is a composition ratio analyzed through FIG. 2a.
Figure 3 is a graph showing the XRD pattern results after the CIGS nanoparticles synthesized according to the present invention coated with molybdenum (Mo) on a soda lime glass plate, and then heat-treated in Ar atmosphere for 30 minutes at 400 ℃.
FIG. 4 is a SEM photograph at 10 times magnification of the CIGS nanoparticles prepared by the method shown in FIG. 1 and then coated in a doctor blade manner.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The embodiments described below may be modified in various forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more fully explain the present invention to those skilled in the art.

An embodiment of the present invention provides a method for producing CIGS-based nanoparticles that can be performed at a relatively low temperature without using a vacuum process to reduce the use time of toxic materials to the maximum. Colloidal (colloidal) method is a typical low-cost I-III-VI solar cell manufacturing process of the manufacturing method that does not use a vacuum process is one of the powder coating method by the fine nanoparticles. When the light absorption layer is manufactured using the synthesized CIGS nanoparticles, it is possible to manufacture low-cost large-area solar cells with a simple manufacturing process.

1 is a process block diagram showing a process of synthesizing CIGS-based nanoparticles according to an embodiment of the present invention. Here, the CIGS-based nanoparticles are in colloidal form.

Referring to FIG. 1, a method of preparing a colloidal CIGS-based nanoparticle may be divided into preparing a raw material, synthesizing the raw material, and removing NaI as an impurity from the synthesized particles. The raw material is prepared in the form of a solution in which iodine compounds of CuI, InI ₃ and GaI ₃ in powder form are mixed with a pyridine solvent and Na ₂ Se is mixed with a methanol solvent. At this time, pyridine and methanol are solvents from which water is removed through dehydration, deoxygenation and distillation.

Here, the temperature of the pyridine solvent is adjusted to be 40 ~ 80 ℃ in order to be able to dissolve the CuI, InI ₃ and GaI ₃ compound in powder form in the pyridine solvent. The temperature is the optimum temperature at which iodine compounds of CuI, InI ₃ and GaI ₃ can be dissolved in a pyridine solvent. Specifically, when the temperature is lower than 40 ℃, the compound is difficult to dissolve in the solvent. In addition, when the temperature is higher than 80 ° C., the solution may be boiled, which may interfere with the nitrogen atmosphere during the reaction, and it is difficult to obtain a proper CIGS composition ratio and yield when the reacted solution boils out of the flask.

The iodine compounds of CuI, InI ₃ and GaI ₃ were mixed with a pyridine solvent and Na ₂ Se with a methanol solvent in an inert atmosphere using nitrogen. On the other hand, the efficiency of the CIGS light absorption layer is known to be highest when Cu, In, Ga, Se have a composition ratio of 1.1, 0.68, 0.23, 1.91, respectively. Accordingly, in the embodiment of the present invention, the synthesis amount of the powder was adjusted in accordance with the composition ratio. That is, about 1.05 g of CuI, about 1.69 g of InI ₃ , about 0.52 g of GaI ₃ , about 1.20 g of Na ₂ Se, about 30 ml of pyridine as a solvent, and about 20 ml of methanol as a solvent. If the reaction is carried out in a nitrogen atmosphere, it can be carried out in a low vacuum unlike the conventional.

Subsequently, the two solutions are mixed to synthesize nanoparticles. To this end, a pyridine solution in which CuI, InI ₃ and GaI ₃ powders are dissolved, and a methanol solution in which Na ₂ Se powder is dissolved are reacted by stirring in an ice bath. The synthesized nanoparticles are colloidal to precipitate CIGS and byproduct NaI. Then stabilize for about 24 hours. Pyridine, the solvent used in the examples of the present invention, is -42.0 ° C at some point. Accordingly, it is not preferable to use a dry ice (-78.0 ° C.) bath proposed in the prior art. This is because when the dry ice bath is used, pyridine is frozen and the synthesis cannot be performed smoothly.

On the other hand, the process of removing the by-product NaI is first separated by CIGS colloid and NaI layer using a centrifuge, then repeated washing using methanol and ultrasonic cleaner to remove the by-product NaI. Accordingly, CIGS nanoparticles from which NaI, which is a byproduct, are removed can be obtained. According to an embodiment of the present invention, CIGS nanoparticles prepared by the above method can be obtained within about 1 hour.

Conventional solvent thermal method is difficult to obtain the required physical properties because it is difficult to seal the reaction vessel toxic amine compound for a long time (20 ~ 60 hours), but according to the CIGS according to an embodiment of the present invention a relatively short one hour Nanoparticles can be obtained within. Alternatively, since the synthesis process is performed at a lower temperature than the conventional one, the manufacturing cost can be reduced.

FIG. 2A shows the composition ratio of the CIGS nanoparticles synthesized according to the embodiment of the present invention on a soda lime glass plate on which molybdenum (Mo) was deposited, and after heat treatment in an Ar atmosphere at 400 ° C. for 30 minutes. This is a graph analyzed. FIG. 2B is a composition ratio analyzed through FIG. 2A. Here, the part which is not hatched is the result of EDX analysis after vapor deposition, and the hatched part is the result of EDX analysis after annealing. At this time, the binder for coating was used by mixing a mixture of ethyl cellulose and alcohol (butyl carbitol) solvent.

As shown, the composition ratio of CIGS is known to be the most efficient at the ratio of Cu _0.98 In _0.68 Ga _0.23 Se _1.91 . CIGS nanoparticles synthesized according to the present invention has a ratio of Cu _0.97 In _0.68 Ga _0.3 Se _1.95 , and after heat treatment, shows a ratio of Cu _0.97 In _0.68 Ga _0.3 Se _1.96 . That is, the CIGS nanoparticles which were stable also by the Example of this invention were obtained. On the other hand, when the CIGS nanoparticles synthesized by the synthesis method described in FIG. 1 is mixed with a binder and coated, it can be used as an absorbing layer that absorbs sunlight.

Figure 3 is a graph showing the XRD pattern results after the CIGS nanoparticles synthesized according to an embodiment of the present invention coated with molybdenum (Mo) soda lime glass plate, and then heat-treated in Ar atmosphere for 30 minutes at 400 ℃. Here, a solid line is an XRD pattern after vapor deposition, and a dashed-dotted line is an XRD pattern after annealing. At this time, the binder for coating was used by mixing a mixture of ethyl cellulose and alcohol (butyl carbitol) solvent. Peaks such as (112), (220), (321), (008) and (332), which are the peaks of CIGS, were observed, and these peaks were chalcopyrate, which is a stable structure of the absorption layer where the CIGS particles absorb sunlight. (chalcopyrite) has a structure.

FIG. 4 is a SEM photograph at 10 times magnification of the CIGS nanoparticles prepared by the method shown in FIG. 1 and then coated in a doctor blade manner. At this time, the binder for coating was used by mixing a mixture of ethyl cellulose and alcohol (butyl carbitol) solvent. In the photograph, the dark part is CIGS nanoparticles, and the light part is a hole. It can be seen that the CIGS particles are coated with a uniform distribution throughout. CIGS nanoparticles prepared by the present invention can easily form a patterned thin film using a suitable mask (Mask).

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, but many variations and modifications may be made without departing from the scope of the present invention. It is possible.

Claims (4)

Preparing a pyridine solution obtained by mixing iodine compounds of CuI, InI ₃ and GaI ₃ in powder form with a pyridine solvent;
Preparing a methanol solution in which Na ₂ Se is mixed with a methanol solvent;
Synthesizing nanoparticles by mixing the pyridine solution and the methanol solution; And
Method for producing a CIS-based nanoparticles comprising the step of removing the by-product NaI. The method of claim 1, wherein the pyridine solution is formed by heating to 40 ~ 80 ℃ CIGS-based nanoparticles manufacturing method. The method of claim 1, wherein the pyridine solution and the methanol solution is formed in an inert atmosphere. The method of claim 1, wherein the synthesizing the nanoparticles by mixing the pyridine solution and the methanol solution is performed in an ice bath.

Images