KR20190132975A - A process of preparing chalcopyrite based thin film - Google Patents

Abstract

The present invention a technology for manufacturing a CIGS thin film using a solution coating method with high cost competitiveness and applying a CIGS thin film to a photovoltaic cell. More specifically, the present invention relates to the technology for manufacturing a high quality CIGSSe thin film by introducing a novel process method to a selenization process, which is a key heat treatment step for synthesizing the CIGSSE thin film with a chalcopyrite structure, to increase the photovoltaic cell efficiency.

Description

A process of preparing chalcopyrite based thin film

The present invention relates to a technology for producing a CIGS thin film and applying it as a solar cell using a solution coating method of high cost, in detail, in the selenization process, which is a core heat treatment step for synthesizing a CIGSSe thin film of a chalcoprite structure The present invention relates to a technology for manufacturing a high quality CIGSSe thin film by introducing a new process method and improving solar cell efficiency.

The technology that obtains electric energy by using light energy of sunlight is considered to be one of the promising renewable energy technologies because of the infinite and environmentally friendly advantages of the sun. The above-mentioned energy conversion requires a device called a solar cell, and in general, solar cell types are divided according to light absorption layer materials that absorb electrons and generate electrons and holes, which are sources of electrical energy.

The solar cells reported so far are largely commercialized, including silicon (Si) solar cells, compound thin film solar cells (CIGS, CdTe), next generation solar cells, dye-sensitized solar cells (DSSCs), organic solar cells (OPV), Organic / inorganic perovskite solar cells (PSCs). As described above, solar cells that reach the commercialization stage are solar cells based on a light absorption layer based on Si or an inorganic compound semiconductor (eg, CIGS). The next-generation solar cells containing other organic materials have various advantages, but they are still in the research stage because they are not highly efficient and they do not have stability and reliability. Level.

Si solar cells have been regarded as representative solar cells that can be practically applied for a long time based on high light conversion efficiency and stability. However, due to the disadvantage of low price competitiveness in the manufacturing process, a lot of development for the compound material with a high light absorption coefficient has been made to replace it. CIGS, a typical compound light-absorbing material, can be manufactured through a thin film because its light absorption coefficient is higher than that of Si. In addition, most of the high quality CIGS thin films have used most of the vacuum sputtering process, which requires expensive equipment and auxiliary devices, but in recent years, high quality light absorbing layer using a solution coating process to increase the price competitiveness of thin film solar cells. Many attempts have been made to obtain thin films. If the CIGS thin film is made thinner and can be converted to Si-like photoelectric conversion efficiency, it can be a viable alternative with excellent price competitiveness.

The CIGS compound light absorbing layer is a chalcopyrite based thin film containing elements of Groups IB, IIIA, and VIA, and generally has a composition of Cu (In, Ga) (S, Se) ₂ . In order to efficiently operate a solar cell, a buffer thin film layer that efficiently transfers excited electrons and holes in response to light is required based on the light absorbing layer. In general, the electron transport layer uses CdS or ZnS, and the hole transport layer uses MoSe ₂ .

One of the important ways to increase the efficiency of CIGS solar cells is to manufacture high quality CIGS light absorbing layer. In general, CIGS thin film manufacturing method using a low-cost solution process is composed of a CIG oxide film through a solution process, a selenization heat treatment by post-treatment, selenization heat treatment to produce a CIGS thin film and improve the crystal quality Various attempts have been reported, such as the introduction method, but in any case, selenization heat treatment is regarded as an essential process for improving the quality of the thin film. Therefore, developing an effective selenization process is a key factor in improving CIGS thin film solar cell efficiency.

Korean Patent Publication No. 10-2012-0115779 Korean Patent Publication No. 10-2013-0077285 Korean Patent Registration No. 10-1438486

One aspect of the present invention is to provide a high quality CIGSSe thin film manufacturing method that can improve the photoelectric conversion efficiency of the solar cell by controlling the crystal growth of the CIGSSe thin film in the thin film.

Another aspect of the present invention is to provide a high quality CIGSSe solar cell manufactured by the above manufacturing method.

One aspect of the present invention is a method for producing a CIGSSe thin film comprising the step of selenization for the selenization target thin film, the selenization target thin film is a CIG thin film or CIGSSe thin film, the selenization treatment is at least two selenium It relates to a method for producing a CIGSSe thin film, characterized in that the selenium is supplied from a source.

According to various embodiments of the present invention, a method for manufacturing high-quality CIGSSe thin films and solar cells may provide selenium vapor through a plurality of Se sources so that selenium vapor may be continuously supplied to a sample during selenization, thereby increasing CIGSSe crystal growth. It is possible to improve the light conversion efficiency of the solar cell by forming the CIGSSe thin film of high quality by helping more efficiently and controlling the heat treatment process conditions.

1 is a schematic diagram of the selenization tube furnace conditions according to an embodiment of the present invention.
2 shows XRD results of thin films prepared in Examples and Comparative Examples.
3 is a graph showing SEM photographs and photocurrent voltage curves of thin films prepared in Examples and Comparative Examples and performance factors of solar cells extracted therefrom.
4 is a graph showing SEM photographs and photocurrent voltage curves of thin films prepared in Examples and Comparative Examples and performance factors of solar cells extracted therefrom.

Hereinafter, various aspects and various embodiments of the present invention will be described in more detail.

According to an aspect of the present invention, a method of manufacturing a CIGSSe thin film comprising the step of selenization for the selenization target thin film, wherein the selenization target thin film is a CIG thin film or CIGS thin film, the selenization treatment is at least two places It relates to a method for producing a CIGSSe thin film, characterized in that the selenium is supplied from the above-mentioned selenium source.

As described above, in the present invention, after forming a CIG oxide film or an incomplete CIGS thin film, in the selenization process for forming a complete CIGSSe thin film or improving the quality of the thin film, a method different from the existing Se supply method is introduced. Inner selenization was made to be more effective.

In one embodiment, the selenium supply from the at least two selenium sources is achieved by raising the respective selenium feed specimens according to different temperature profiles in the at least two selenium sources.

In another embodiment, the selenium feed specimen may be selected from pellets, powders, granules or mixtures thereof, but is not limited thereto.

In another embodiment, the selenization treatment has the selenide thin film in the tubular reactor for selenization, a plurality of selenium supplied to a position at a different distance in the longitudinal direction of the tubular reactor from the selenide thin film After placing the specimen, each selenium is heated up according to a different temperature profile.

In another embodiment, the selenization treatment has the selenide thin film in the tube for selenization, and the first selenium supply point and the second selenium supply point, respectively, at different distances from the selenization target thin film. After placing the selenium supply specimen and the second selenium supply specimen, the first selenium supply specimen is heated by heat treatment with the thin film to be selenized, and the second selenium supply specimen is heated up after a predetermined time after the start of the heat treatment.

In another embodiment, the temporal section of the selenium supply is a selenium supply section through the first selenium supply point only, the selenium supply section through both the first selenium supply point and the second selenium supply point, the second selenium It consists of a supply of selenium through a supply point only.

In this case, the first selenium supply point may be located relatively close to the selenide thin film, and the second selenium supply point may be located relatively far from the selenide thin film.

In addition, the predetermined time may vary depending on the conditions such as the amount of the selenium supply specimen and the area of the thin film to be selenium, preferably 5 to 30 minutes, more preferably 10 to 20 minutes.

In another embodiment, the first selenium supply point is at a distance of 1 ~ 20cm from the selenization target thin film, the second selenium supply point is at a distance of 10 ~ 100cm from the selenide target thin film, The distance between the first selenium supply point and the second selenium supply point is 10-50 cm.

In another embodiment, the selenization target thin film is a CIG thin film, and the selenization treatment is performed simultaneously with the sulfiding treatment of the CIG thin film.

In another embodiment, the selenization treatment performed simultaneously with the sulfiding treatment is performed by performing the selenization treatment in a mixed gas atmosphere of hydrogen sulfide and a carrier gas.

In another embodiment, the selenization treatment has the selenide thin film in the tube for selenization, and the first selenium supply point and the second selenium supply point, respectively, at different distances from the selenization target thin film. After placing the selenium supply specimen and the second selenium supply specimen, each selenium is heated up according to a different temperature profile. In addition, when the amount of selenium remaining through the first supply of selenium decreases to 5 to 99% of the amount initially supplied, the supply of the second selenium supply point is greater than the amount of supply of selenium per unit time through the first supply of selenium. The supply of selenium per unit time is greater.

In another embodiment, the first selenium feed specimen is heated to 400 ~ 440 ℃ at a rate of 10 ~ 20 ℃ and then heated up at a rate of 3 ~ 7 ℃ / min to 450 ~ 490 ℃ constant temperature The second selenium supply test piece is heated to about 480-570 ° C. at a rate of 10-20 ° C. at 8-12 minutes before the first selenium supply test piece reaches 420 ° C.

In another embodiment, (i) initiating the supply of selenium through the second selenium supply point 10-20 minutes after the start of supplying selenium through the first selenium supply point (ie, starting the heat treatment of the thin film to be selenized). (Ii) the first selenium supply point is at a distance of 5 to 10 cm from the thin film for selenization, and the second selenium supply point is at a distance of 15 to 30 cm from the thin film for selenization, and the first The distance between the selenium supply point and the second selenium supply point is 7 to 20 cm, and (iii) the selenization target thin film is a CIG thin film, and the selenization treatment is sulfiding through a mixed gas of hydrogen sulfide and nitrogen of the CIG thin film. And (iv) selenium balls per unit time through the first selenium feed point at a point where the remaining amount of selenium through the first selenium feed point is reduced to 80-95% of the amount initially supplied. And supplying selenium through the second selenium supply point such that the amount of selenium per unit time through the second selenium supply point is greater than the amount thereof, and (v) the first selenium supply specimen is 400 to 400 ° C at a rate of 10 to 20 ° C. After the temperature was raised to 440 ° C., the temperature was increased to 450 to 490 ° C. at a rate of 3 to 7 ° C./minute, and then the temperature was kept constant. The second selenium supply test piece was used to achieve the first selenium supply test piece to reach 420 ° C. 8 It heats up to about 480-570 degreeC at the speed of 10-20 degreeC about -12 minutes ago.

It is important to satisfy all of the above conditions (i) to (v), and if any one of these conditions is not satisfied, selenium vapors supplied from the second selenium supply point are agglomerated with each other, so that the high-quality selenium thin film (I) to (v) in that the selenium morphology may be undesirably formed in the selenium target thin film, so that the efficiency of the photoactive layer may not be improved. The fulfillment of conditions is important.

According to another aspect of the present invention, in the selenization target thin film selected from the CIG thin film or CIGS thin film according to various embodiments of the present invention, the selenium target to adjust the angle between the selenium supply point and the selenium target thin film It relates to a method for controlling selenization of a thin film.

According to various embodiments of the present invention, a dual structure furnace is used to simultaneously achieve rapid selenization in the early stages and continuous selenization in the mid to late stages. The first selenization was carried out by raising the sample to be selenized, and another selenium source was heated in the mid-to-late heat treatment step in which the selenium source was almost exhausted so that the selenium vapor could be continuously supplied to the sample.

In addition to the continuous selenium supply, the selenization method through the plurality of selenium sources has the following advantages. In the conventional method, since selenide vapor is supplied to the substrate from only one source (temperature zone 1 or zone 2 in FIG. 1), the selenium source is exhausted so quickly that incomplete selenization proceeds (in case of zone 1), or Due to the temperature gradients in regions 1 and 2, aggregation of selenium atoms or molecules is more likely to cause selenium vapors to react with the sample, making it difficult to achieve complete selenization and produce high quality CIGS thin films. According to the method proposed by the present invention, in the initial stage, selenium vapor is supplied near the substrate (temperature region 1) to react with the sample thin film more efficiently because the selenium vapor having a small molecular size is reacted.

In addition, an increase in the pressure of selenium vapor near the substrate (temperature region 1) is another advantage. Since additional selenium was supplied near the substrate (temperature zone 1), the pressure of selenium vapor reacted with the sample thin film relatively increased, and as a result, the selenium vapor diffused to a deeper region, thus making the crystal of CIGS thin film more efficient. To help you grow.

In addition, in the mid- and late stages, selenium vapor is supplied from the selenium source in the temperature zone 2 and the selenium supply is continuously performed until all selenization heat treatments are completed, thereby achieving complete selenization of the sample thin film. By controlling the supply of selenium, the composition of the thin film can be induced to produce a high efficiency thin film.

Hereinafter, the present invention will be described in more detail with reference to examples and the like, but the scope and contents of the present invention are not limited or interpreted by the following examples. In addition, if it is based on the disclosure of the present invention including the following examples, it will be apparent that those skilled in the art can easily carry out the present invention, the results of which are not specifically presented experimental results, these modifications and modifications are attached to the patent It goes without saying that it belongs to the claims.

In addition, the experimental results presented below are only representative of the experimental results of the Examples and Comparative Examples, and the effects of each of the various embodiments of the present invention not explicitly set forth below will be described in detail in the corresponding sections.

Example

Example  1: through dual supply of selenium CIGSSe  Manufacture of thin film

A CIGS thin film was prepared by selenization of a CIG oxide thin film made by spin coating a solution-based precursor. First, a CIG oxide thin film was prepared by spin-coating a paste in which precursors of Cu, In, and Ga were dissolved in methanol together with a binder on a soda-lime glass on which Mo was deposited, and heat-treating under atmospheric conditions.

The resulting CIG oxide thin film was then placed in a tube furnace as shown in FIG. 1 to produce a CIGSSe light absorbing layer via selenization. Of the two temperature zones located at a distance of about 15 cm, the temperature zone 1 on the left side was independently controlled by the temperature of the thin film sample and the temperature zone 2 on the right side was controlled by the temperature of the Se source. In this way, the Se source is placed in two temperature zones (two-stage selenization) and the selenium thin film (sample) is tilted in the temperature zones (1) and (2) directions so that the selenium vapor is more easily contacted. By doing so, CIGS crystal growth was made more efficient.

1 is a schematic diagram showing a differentiated selenization method according to the present invention. A sample coated with a thin film of CIG oxide on Mo-soda lime glass was placed in the temperature zone 1, and 0.5 g of each of the Se pellets was placed in the temperature zone 1 and the temperature zone 2 as the Se source. A mixed gas of sulfide gas and nitrogen (H ₂ S / N ₂ ) was used as a background gas, and the mixture was allowed to flow for 15 minutes before the reaction to stabilize the atmosphere.

First, the temperature of the temperature zone 1 is raised to 420 ° C. at a rate of 16.8 ° C./min, stepped up to 450 ° C. at a rate of 6 ° C./min, and then raised to 470 ° C. at a rate of 4 ° C./min 15 Hold for a minute. Ten minutes before the temperature of the temperature region 1 reached 420 degreeC, the temperature of the temperature region 2 was heated up to about 550 degreeC at 15 degree-C / min speed, and it maintained for about 50 minutes. After the reaction was completed, the temperature in the tube was slowly dropped to room temperature.

XRD was measured to confirm the crystal growth degree of the CIGSSe thin film thus prepared (FIG. 2), and the intensity of the peak (near 2θ = 27 ^o ) corresponding to the CIGSSe light absorbing layer was larger than that of the conventional CIGSSe thin film. It was confirmed that this is a result showing that the crystal of the CIGSSe light absorbing layer was further grown.

As a result of confirming the SEM image (FIGS. 3A to 3F), it was confirmed that the grains of the CIGSSe light absorbing layer supplied with Se through the double source were grown larger, deeper and more compactly.

Even in the efficiency of the prepared light absorbing layer produced by the solar cell (Figs. 3g and 3h), it can be seen that the 7.8% increase compared to the control. The main reason for the increase in efficiency is the increase in the photocurrent, which seems to affect the photocurrent due to more efficient crystal growth of the light absorption layer.

Example  2 and Example  3: through double supply of selenium CIGSSe  Manufacture of thin film

The selenization heat treatment conditions of Example 1 were changed to optimize the growth of high quality CIGSSe thin film. In Example 1 above, the temperature condition of the temperature region 2 was maintained as it is, and the time and temperature conditions of the heat treatment process in the temperature region 1 were changed as follows.

First, in Example 1, the temperature of the temperature zone 1 is maintained at 470 ° C. for 15 minutes, while the temperature zone 2 is raised to 500 ° C. instead of 550 ° C. for 15 minutes. Except for, a CIGSSe thin film was prepared in the same manner as in Example 1 (Example 2). In addition, a CIGSSe thin film was prepared in the same manner as in Example 1 except that the temperature was maintained for 45 minutes instead of 15 minutes at 470 ° C. in Example 1 (Example 3).

Test Example  1 to 3

The SEM photographs and the efficiencies of the CIGSSe thin films prepared in Examples 1 to 3 are shown in FIG. 4. As the crystal growth increases, the efficiency is relatively high, but when the growth is excessive, the efficiency decreases, and it is confirmed that there is an optimized degree of crystal growth. These results are believed to be due to the trade-off of the non-ideal distribution of Se-rich light-absorbing layer bandgap as well as the efficient flow of electrons and holes generated by light-absorption into the grains. do.

Comparative example Through a single supply of selenium CIGSSe  Manufacture of thin film

A CIGSSe thin film was prepared in the same manner as in Example 1 except that Se was supplied only in the temperature region 2. The degree of crystal growth of CIGSSe and the resulting photovoltaic cell photoconversion efficiency of the thin films obtained under different conditions were compared, and the results are shown in FIGS. 2 to 4.

As a result of the above experiment, it was confirmed that by introducing the selenization process according to the present invention, the solar cell efficiency can be increased by about 7.8% compared with the case of the conventional method.

Claims (13)

(A) A method for producing a CIGSSe thin film comprising the step of selenization treatment for the selenization target thin film,
The selenide target thin film is a CIG thin film or CIGS thin film,
The selenization process is a method for producing a CIGSSe thin film, characterized in that the selenium is supplied from at least two sources of selenium. The method of claim 1, wherein the selenium supply from the at least two selenium sources is achieved by raising the respective selenium feed specimens according to different temperature profiles from the at least two selenium sources. According to claim 2, The selenization treatment is a plurality of selenium supplying specimens in the selenization tube-type reactor in the selenization tube thin film at the position of a different distance in the longitudinal direction of the tubular reactor from the selenization target thin film After positioning the selenium according to a different temperature profile, the method of producing a CIGSSe thin film, characterized in that the made. 4. The selenization process of claim 3, wherein the selenization treatment includes placing the selenide thin film in a tube for selenization and relatively far from the first selenium supply point located relatively close to the selenide thin film and the selenide thin film. After placing the first selenium supply specimen and the second selenium supply specimen at the second selenium supply point located,
The first selenium supply specimen is heated by heat treatment with the thin film to be selenide,
The second selenium supply test piece is a method for producing a CIGSSe thin film, characterized in that to increase the temperature after a certain time after the start of the heat treatment.
The predetermined time may vary depending on conditions such as the amount of the selenium supply specimen and the area of the thin film to be selenized, but is preferably 5 to 30 minutes, more preferably 10 to 20 minutes. The method of claim 4, wherein the temporal interval of the selenium supply is a selenium supply section through the first selenium supply point only, a selenium supply section through both the first selenium supply point and the second selenium supply point, and the second selenium supply. Method for producing a CIGSSE thin film, characterized in that consisting of the selenium supply section through the point only. The method of claim 5, wherein the first selenium supply point is a distance of 1 ~ 20cm from the thin film to be selenization, the second selenium supply point is a distance of 10 ~ 100cm from the thin film to be selenide, 1 The distance between the selenium supply point and the second selenium supply point is a method for producing a CIGSSe thin film, characterized in that 10 ~ 50cm. The thin film according to any one of claims 1 to 6, wherein the selenization target thin film is a CIG thin film,
Said selenide treatment is a method for producing a CIGSSe thin film, characterized in that is carried out simultaneously with the sulfidation of the CIG thin film. The method of claim 7, wherein the selenization treatment performed simultaneously with the sulfiding treatment is performed by performing the selenization treatment in a mixed gas atmosphere of hydrogen sulfide and a carrier gas. The selenium treatment of claim 8, wherein the selenization treatment comprises placing the selenide thin film in a tube for selenization, and the first selenium at the first selenium supply point and the second selenium supply point, respectively, at different distances from the selenization target thin film. By placing the feed specimen and the second selenium feed specimen, each of the selenium is heated according to a different temperature profile,
Residual amount of selenium through the first selenium supply point is reduced to 5 to 99% of the initially supplied amount of unit time through the second selenium supply point than the amount of selenium per unit time through the first selenium supply point A method for producing a CIGSSe thin film, characterized in that the supply of sugar selenium is larger. 10. The method of claim 9, wherein the selenization treatment includes placing the selenide thin film in a tube for selenization, and the first selenium at the first selenium supply point and the second selenium supply point, respectively, at different distances from the selenization target thin film. By placing the feed specimen and the second selenium feed specimen, each of the selenium is heated according to a different temperature profile,
The first selenium supply specimen is heated to 400 ~ 440 ℃ at a rate of 10 ~ 20 ℃ and then heated up at a rate of 3 ~ 7 ℃ / min to 450 ~ 490 ℃ and then maintained a constant temperature, the second selenium The supply specimen is a method for producing a CIGSSe thin film, characterized in that the temperature is raised to about 480 ~ 570 ℃ at a rate of 10 ~ 20 ℃ 8 to 12 minutes before the first selenium supply specimen reaches 420 ℃. The method of claim 10, further comprising: (i) starting selenium supply through the second selenium supply point 10 to 20 minutes after the start of supplying selenium through the first selenium supply point or starting the heat treatment of the selenium thin film;
(ii) the first selenium supply point is at a distance of 5 to 10 cm from the thin film for selenization, and the second selenium supply point is at a distance of 15 to 30 cm from the thin film for selenization, and the first selenium supply is performed. The distance between the point and the second selenium supply point is 7-20 cm,
(iii) the selenide target thin film is a CIG thin film, and the selenization treatment is performed simultaneously with the sulfiding process through a mixed gas of hydrogen sulfide and nitrogen of the CIG thin film,
(iv) the second selenium supply point than the amount of selenium per unit time through the first selenium supply point at a time when the remaining amount of selenium through the first selenium supply point is reduced to 80 to 95% of the amount initially supplied; Supplying selenium through the second selenium supply point so that the amount of selenium supplied per unit time through
(v) the first selenium supply specimen is heated to 400 ~ 440 ℃ at a rate of 10 ~ 20 ℃ and then heated up at a rate of 3 ~ 7 ℃ / min to 450 ~ 490 ℃ and then maintained a constant temperature, The second selenium supply specimen is a method for producing a CIGSSe thin film, characterized in that the temperature is raised to about 480 ~ 570 ℃ at a rate of 10 ~ 20 ℃ 8 to 12 minutes before the first selenium supply specimen to reach 420 ℃. A method of controlling selenization of the selenization target thin film by controlling the angle between the selenium supply point and the selenization target thin film in selenization target thin film selected from a CIG thin film or a CIGS thin film. The method of claim 12, wherein the selenization treatment includes placing the selenide thin film in a tube for selenization and relatively far from the first selenium supply point located relatively close to the selenide thin film and the selenide thin film. Selenium is performed by placing the first selenium supply specimen and the second selenium supply specimen at the second selenium supply point located, and then heating the first selenium supply specimen and the selenium supply specimen to different temperature profiles. How to control anger.

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