KR102328949B1 - Composite Thin Film Structure with Improved Thermal Performance and Its Manufacturing Methods - Google Patents

Abstract

Provided are a composite thin film structure with improved thermoelectric performance and a manufacturing method. The manufacturing method of the composite thin film structure comprises the steps of preparing a base source comprising a block copolymer comprising a block A and a block B, and a nanowire, on a substrate, by providing the base source to form a composite thin film Step, providing a vapor in which a solvent for selectively removing the block B from the block copolymer is vaporized on the composite thin film, and removing at least a portion of the block B in the composite thin film.

Description

Composite Thin Film Structure with Improved Thermal Performance and Its Manufacturing Methods

The present application relates to a composite thin film structure with improved thermoelectric performance and a method for manufacturing the same, and more particularly, to a composite thin film structure with improved thermoelectric performance according to a difference in energy level between a block copolymer and a nanowire, and a method for manufacturing the same will be.

The use of fossil fuels is being pointed out as the main culprit of the rapid increase in energy demand and climate change, and efforts are being made to secure alternative energy sources worldwide. Petroleum, the largest energy source, is subject to considerable restrictions due to limitations in oil reserves and mining, political instability in oil-producing countries, and cost increases due to increased supply of deep-sea oil fields. Accordingly, efforts are being made to secure alternative energy sources worldwide to replace existing fossil fuels such as petroleum. However, as the safety of nuclear power, which has been evaluated as the most economical alternative energy source, has been raised due to the Fukushima nuclear accident, there is a movement to stop or reduce the construction of nuclear power plants worldwide. In addition, alternative energies such as solar power, wind power, and tidal power are no longer making great progress due to limitations in technological progress and lack of economic feasibility.

Recently, energy harvesting, which improves fuel efficiency by recovering waste heat and converting it into electrical energy, is attracting attention rather than developing alternative energy. A thermoelectric element is an element used to directly convert thermal energy into electric energy and electric energy into thermal energy. It is widely used in industries such as automobiles, space, aviation, semiconductors, bio, optics, computers, power generation, and home appliances. Developed countries are conducting research on thermoelectric materials to improve fuel efficiency centering on research institutes and companies, and in Korea, research centers and universities are also conducting research on thermoelectric materials.

Accordingly, various techniques for manufacturing a composite thin film structure with improved thermoelectric performance have been studied. For example, in the Republic of Korea Patent Registration Publication KR 1020561490000 (application number KR 1020170184337 Applicant: Hanbat University Industry-University Cooperation Foundation, Korea Institute of Science and Technology), a thermoelectric material sintered body having a flat upper surface and a lower surface and a side surface including a curved surface is applied. A metal bar positioned between an upper surface of one unit and a lower surface of another adjacent to the one unit, and in contact with each of the upper surface of the one unit and the lower surface of the other unit through a metal bonding member and providing a laminate comprising an insulating pad positioned in a space between the upper surface of the one unit and the lower surface of the other unit; and applying a current while physically pressing the laminate to the laminate. Disclosed is a technology for manufacturing a curved thermoelectric device, including manufacturing a thermoelectric device in which each unit included in a sieve, a metal bonding member, and a metal bar are integrally cut. In addition, technologies related to a thermoelectric element and a method for manufacturing the same are continuously being studied.

One technical problem to be solved by the present invention is to provide a composite thin film structure with improved thermoelectric performance and a method for manufacturing the same.

Another technical problem to be solved by the present invention is to prepare a composite thin film structure capable of controlling the energy level difference value between the Fermi level of the block copolymer and the valence band of the nanowire, and a method for manufacturing the same.

One technical problem to be solved by the present invention is to provide a composite thin film structure in which a manufacturing process is simplified and a manufacturing method thereof.

One technical problem to be solved by the present invention is to provide a composite thin film structure with reduced manufacturing cost and a method for manufacturing the same.

One technical problem to be solved by the present invention is to provide a composite thin film structure having high reliability and a method for manufacturing the same.

One technical problem to be solved by the present invention is to provide a composite thin film structure having a long lifespan and a method for manufacturing the same.

The technical problem to be solved by the present invention is not limited to the above.

In order to solve the above-described technical problems, the present invention provides a method for manufacturing a composite thin film structure.

According to an embodiment, the method for manufacturing the composite thin film structure includes the steps of preparing a base source including the block copolymer including the block A and the block B, and the nanowire, on the substrate, the Forming the composite thin film by providing a base source, providing a vapor in which a solvent for selectively removing the block B from the block copolymer is vaporized to the composite thin film, so that at least of the block B in the composite thin film It may include providing a composite thin film structure comprising the step of removing a portion.

According to an embodiment, the solvent may include a polar solvent, and the polar solvent includes at least one of DMSO (dimethyl sulfoxide), EG (ethylene glycol), DMF (dimethyl formamide), or MeOH (Methanol). can do.

According to one embodiment, while the vapor in which the solvent is vaporized is provided to the composite thin film, it may include heat-treating.

According to an embodiment, a difference in energy level between a Fermi level of the block copolymer and a valence band of the nanowire may be controlled by the heat treatment time.

According to an embodiment, when heat treatment is performed for 120 minutes, the Seebeck coefficient may have a maximum value.

According to an embodiment, the removal rate of the block B from the block copolymer is controlled by the heat treatment time, and the Seebeck coefficient of the composite thin film is controlled according to the removal rate of the block B. .

According to an embodiment, while the heat treatment is performed for a reference time, the block A and the block B are separated, and after the reference time, the separated block B is controlled, so that the Fermi level of the block copolymer (Fermi level) ) may include a decrease in the density of states in the vicinity.

According to one embodiment, as the block B is removed, it may include reducing the thickness of the composite thin film.

In order to solve the above technical problems, the present invention provides a composite thin film structure capable of adjusting the energy level difference value.

According to an embodiment, the composite thin film structure is a substrate, a composite thin film disposed on the substrate, and a composite thin film including a block copolymer of block A and block B and a nanowire, a Fermi level of the block copolymer and and that an energy level difference is provided between valence bands of the nanowire, and an energy barrier is formed due to the energy level difference, so that a carrier having a low energy is a valence band of the nanowire by the energy barrier Transport is selectively prevented, and carriers having high energy may include transport to a valence band of the nanowire.

According to an embodiment, the block A includes PEDOT, the block B includes PSS, the block copolymer includes PEDOT:PSS, and the nanowire is Bi ₂ Te ₃ nanowire may include

According to an embodiment, the energy level difference may include 0.11 eV to 0.12 eV.

According to an embodiment, the composite thin film includes a lower surface adjacent to the substrate and an upper surface opposing the lower surface, and the lower region adjacent to the lower surface of the composite thin film is on the upper surface of the composite thin film. It may include a block B having a higher ratio than the adjacent upper area.

According to the present invention, the composite thin film structure may include a substrate, a composite thin film disposed on the substrate, and a block copolymer of block A and block B and a nanowire. At least a portion of the block B in the composite thin film may be removed by providing a vapor in which a solvent for selectively removing the block B from the block copolymer is vaporized on the composite thin film. As at least a portion of the block B is removed, an energy level difference is provided between the Fermi level of the block copolymer and the valence band of the nanowire, and the Seebeck coefficient becomes can be controlled. For example, when the heat treatment time is 120 minutes, the Seebeck coefficient may have a maximum value.

1 is a flowchart illustrating a method of manufacturing a composite thin film with improved thermoelectric performance according to an embodiment of the present invention.
2 to 4 are cross-sectional views of a process according to an embodiment of the present invention.
5 to 6 are views showing a manufacturing process of the composite thin film structure according to an embodiment of the present invention.
7 is a view of taking an image for explaining the internal structure of the composite thin film according to an embodiment of the present invention.
8 to 11 are graphs comparing the characteristics of the composite thin film structure according to the heat treatment process time of the composite thin film according to an embodiment of the present invention.
12 is a graph of work function values according to PSS and PEDOT ratios of the composite thin film according to an embodiment of the present invention.
13 is a view showing changes in PEDOT:PSS structure and work function values according to the duration of a heat treatment process according to an embodiment of the present invention.
14 is a graph showing a difference between a Seebeck coefficient and an energy level that changes according to a time for performing heat treatment and fixing according to an experimental example of the present invention.
15 is a schematic band diagram of a composite thin film having an energy barrier and a composite thin film without an energy barrier due to a difference in energy level according to an experimental example of the present invention.
16 is a graph showing the electrical conductivity of the composite thin film structure according to an experimental example of the present invention.
17 is a graph showing the thermoelectric power factor (power factor) of the composite thin film structure according to an experimental example of the present invention.
18 is a grazing incident wide-angle X-ray (GIWAXS) pattern of a _{PEDOT:PSS/Bi 2} Te ₃ nanowire composite thin film in which the heat treatment process execution time is 0, 10, and 120 minutes according to an experimental example of the present invention. .
19 is a graph for showing results according to an experimental example of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the technical spirit of the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided so that the disclosed content may be thorough and complete, and the spirit of the present invention may be sufficiently conveyed to those skilled in the art.

In this specification, when a component is referred to as being on another component, it may be directly formed on the other component or a third component may be interposed therebetween. In addition, in the drawings, thicknesses of films and regions are exaggerated for effective description of technical content.

In addition, in various embodiments of the present specification, terms such as first, second, third, etc. are used to describe various components, but these components should not be limited by these terms. These terms are only used to distinguish one component from another. Accordingly, what is referred to as a first component in one embodiment may be referred to as a second component in another embodiment. Each embodiment described and illustrated herein also includes a complementary embodiment thereof. In addition, in the present specification, 'and/or' is used to mean including at least one of the elements listed before and after.

In the specification, the singular expression includes the plural expression unless the context clearly dictates otherwise. In addition, terms such as "comprise" or "have" are intended to designate that a feature, number, step, element, or a combination thereof described in the specification is present, and one or more other features, numbers, steps, configuration It should not be construed as excluding the possibility of the presence or addition of elements or combinations thereof.

In addition, in the following description of the present invention, if it is determined that a detailed description of a related well-known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

1 is a flowchart for manufacturing a composite thin film structure according to an embodiment of the present invention, and FIGS. 2 to 4 are process cross-sectional views of the composite thin film structure according to an embodiment of the present invention.

Referring to FIGS. 1 and 2 , a base source including a block copolymer including a block A 120 and a block B 130 and a nanowire 140 is prepared ( S100 ).

For example, the block A 120 may include poly(3,4-ethylenedioxythiophene) (PEDOT), the block B 130 may include polystyrene sulfonate (PSS), and the block copolymer may include PEDOT:PSS. The nanowire 140 may include a Bi ₂ Te ₃ nanowire 140 .

For example, preparing the base source may include dispersing the nanowire 140 in a solvent, and uniformly mixing the block copolymer and the nanowire 140 through a sonicator. It may include the step of preparing a solution. For example, the base source may be formed of a PEDOT:PSS/Bi ₂ Te ₃ nanowire mixed solution in which _{the Bi 2} Te _{3 nanowire 140 is 20 wt%.} For example, the solvent may include ethanol.

The substrate is prepared. For example, the substrate 100 may include a glass substrate. As another example, the substrate 100 may be a silicon semiconductor substrate, a compound semiconductor substrate, or a plastic substrate. The type of the substrate 100 is not limited.

The composite thin film 110 is formed on the substrate 100 by providing the base source (S110).

According to an embodiment, the base source may be provided on the substrate 100 through a spin coating process. For example, the PEDOT:PSS/Bi ₂ Te ₃ nanowire solution is coated twice at 3000 rpm for 30 seconds on a 1X1cm 2 glass substrate. According to another embodiment, the method of providing the base source on the substrate is spray coating, paint bruching, doctor blade, dip drawing, dip coating ( dip coating), diffusion coating, SermeTel Coating, sol-gel coating, roller coating, and flow coating. The type of the process is not limited.

The composite thin film 110 may include the block copolymer including the block A 120 and the block B 130 , and may include the nanowire 140 . In addition, the composite thin film 110 is formed on the substrate 100 in a form in which the block copolymer and the nanowire 140 are mixed.

Referring to FIGS. 1 and 3 , a vapor in which a solvent for selectively removing the block B 130 from the block copolymer is vaporized is provided to the composite thin film 110 ( S120 ).

More specifically, the step of providing the vapor to the composite thin film 110 includes providing the substrate 100 coated with the solvent and the composite thin film 110 in an airtight container, and the solvent and the composite It may include applying heat to the substrate coated with the thin film 110 to form the vapor in which the solvent is vaporized, and providing the vapor in which the solvent is vaporized to the composite thin film 110 . .

As described above, the vapor may selectively remove the block B 130 . When the block A 120 is PEDOT, the block B 130 is PSS, the block copolymer is PEDOT:PSS, and the nanowire 140 is Bi ₂ Te ₃ nanowire, the block B 130 ), which selectively removes PSS, may be a vapor obtained by vaporizing a polar solvent. For example, the polar solvent may include dimethyl sulfoxide (DMSO). As another example, the polar solvent may include at least one of ethlene glycol (EG), dimethyl formamide (DMF), and methanol (MeOH). As long as the solvent selectively removes the block B 130 , the type of the solvent is not limited.

1 and 4, at least a portion of the block B 130 in the composite thin film 110 is removed (S130).

As described above, the vapor in which the solvent is vaporized may be provided to the composite thin film 110 . In addition, in a state in which the steam is provided, a heat treatment process may be performed.

During the initial reaction time of the heat treatment process, the block A 120 and the block B 130 may be separated and phase separation may occur. For example, the initial reaction time may be 30 minutes. The composite thin film 110 may include a lower surface adjacent to the substrate 110 and an upper surface facing the lower surface. Due to the phase separation of the block A 120 and the block B 130 , the block B 130 may move to the upper surface of the composite thin film 110 during the initial reaction time. Accordingly, in the composite thin film 110 in which the phase separation has occurred, the ratio of the block B 130 in the upper region adjacent to the upper surface may be relatively higher than that in the lower region adjacent to the lower surface.

After the initial reaction time of the heat treatment process, droplets are formed by condensation of the vapor on the upper surface of the composite thin film 110 . As described above, the block B 130 may be concentrated in the upper region of the composite thin film 110 . Accordingly, at least a portion of the block B 130 in the upper region may be selectively removed by the droplets condensed on the composite thin film 110 . According to an embodiment, substantially all of the block B 130 in the upper region may be removed. Accordingly, in the composite thin film 110 , the ratio of the block B 130 in the lower region may be relatively higher than that in the upper region. As the block B 130 concentrated in the upper region is removed (dissolved), the thickness of the composite thin film 110 may be reduced. In addition, a density of states near a Fermi level of the composite thin film 110 may be reduced.

As described above, after the initial reaction time, the removal rate of the block B 130 is controlled according to the time of the heat treatment process. The time of the heat treatment process may be 90 minutes or more.

On the other hand, when the heat treatment process is performed for 90 minutes or less, a low Seebeck coefficient and thermoelectric characteristics may be obtained. Accordingly, according to an embodiment of the present invention, the heat treatment process may be performed for more than 90 minutes. For example, the heat treatment process may be performed for 120 minutes.

According to the removal rate of the block B 130 , the energy level difference between the Fermi level of the block copolymer and the valence band of the nanowire 140 may be adjusted. A difference between the work function value of the block copolymer and the work function value of the nanowire 140 may be an energy level difference value.

The difference between the Fermi level of the block copolymer and the work function value of the valence band of the nanowire 140 may be controlled according to the time of the heat treatment process. The work function value of the block copolymer is determined according to the removal rate of the block B 130 , and the work function value of the nanowire 140 may be a fixed value. In the case of the Bi ₂ Te ₃ nanowire 140 , the work function value of the nanowire 140 may be 4.82 eV.

Specifically, as the time of the heat treatment process increases, the work function value of the block copolymer may be decreased. Accordingly, as the time of the heat treatment process increases, the difference between the work function values of the block copolymer and the nanowire 140 may increase.

When heat-treated for a short time and the work function value of the nanowire 140 is higher than the work function value of the block copolymer, the valence band of the nanowire 140 is upwardly banded. An energy barrier may not be formed between a Fermi level and a valence band of the nanowire 140 . Accordingly, not only carriers having high energy but also carriers having low energy may be easily transported to the valence band. Accordingly, it may not be easy to increase the Seebeck coefficient of the composite thin film 110 . For example, when the heat treatment process time is less than 90 minutes, the Seebeck coefficient may have a low value.

On the other hand, when the work function value of the block copolymer is higher than the work function value of the nanowire 140 by heat treatment for a long time, an energy filtering effect may appear. The energy filtering effect is that the energy barrier is formed in a different band structure between the Fermi level of the block copolymer and the valence band of the nanowire 140, so that the energy barrier is higher than the energy barrier. Carriers with high energy are transported to the valence band, and carriers with low energy compared to the energy barrier collide with the barrier and disperse. The energy barrier may be formed by downward bending of a valence band of the nanowire 140 . According to the energy filtering effect between the Fermi level of the block copolymer and the valence band of the nanowire 140, the low energy carriers are selectively dispersed by the Fermi level and , the high energy carrier capable of effectively transporting heat compared to the low energy carrier is transported to a valence band of the nanowire 140 , so that the Seebeck coefficient may be increased. For example, if heat treatment is performed for 90 minutes or more, the Seebeck coefficient may increase.

As described above, the block B 130 may be removed by heat treatment for 90 minutes or longer, and as described above, an optimal energy level difference may be generated so that the Seebeck coefficient may have a maximum value. For example, when the heat treatment process time is 120 minutes, the energy level difference may be 0.11 eV, and the Seebeck coefficient may have a maximum value of 47 μV/K. Accordingly, the value of the thermoelectric power factor may be the maximum. By the thermoelectric power factor having the maximum value, the composite thin film structure having improved thermoelectric performance may be manufactured.

According to an embodiment of the present invention, on the composite thin film 110 formed of the block copolymer and the nanowire 140 including the block A 120 and the block B 130, the block B ( 130) may be provided by vaporizing the solvent capable of selectively removing the vapor. During the execution time of the heat treatment process of applying heat to the substrate, the block B 130 may be selectively removed by the vapor. Accordingly, the Seebeck coefficient of the composite thin film may be improved, and thermoelectric properties may be improved.

In addition, the removal rate at which the block B 130 is selectively removed may be determined by the execution time of the heat treatment process, and according to the removal rate of the block B 130 , the Fermi level of the block copolymer and the The energy level difference between the valence bands of the nanowire 140 may be controlled to be 0.11 eV. Accordingly, the Seebeck coefficient of the composite thin film may increase, and thermoelectric properties may be improved.

Hereinafter, the characteristic evaluation result of the composite thin film structure according to a specific experimental example of the present invention will be described.

Preparation of a composite thin film structure according to an experimental example

5 is a view for explaining the coating and heat treatment process of the composite thin film structure according to an experimental example of the present invention.

Referring to FIG. 5 , a glass substrate was prepared as a substrate, PEDOT: PSS was prepared as a block copolymer, and Bi ₂ Te ₃ nanowires were prepared.

The PEDOT: PSS and the Bi ₂ Te ₃ nanowire were mixed with an ultrasonic disperser (sonicator) to prepare a PEDOT:PSS/Bi ₂ Te ₃ nanowire mixed solution in which _{the ratio of the Bi 2} Te _{3 nanowire was 20%.} . The mixed solution was spin-coated twice at 3000 rpm for 30 seconds on the glass substrate having a size of 1×1 cm 2 . Accordingly, a composite thin film was formed on the glass substrate.

DMSO (dimethyl sulfoxide) was prepared as a polar solvent. To vaporize 0.2 mL of DMSO, the polar solvent, the lid of the vial was closed and heat was applied at 170° C. for 1 minute. Thereafter, the spin-coated composite thin film was subjected to a heat treatment process at various times of 5, 10, 20, 30, 60, 90, 120, 180 and 240 minutes in a wet state under DMSO vapor at 170°C. After the heat treatment process, annealing at 150° C. for 30 minutes to remove the residual solvent, a composite thin film structure according to Experimental Example 1 was prepared.

6 is a view for explaining a change in the PSS removal rate according to the heat treatment process time of the composite thin film structure according to the experimental example of the present invention.

Referring to FIG. 6 , phase separation of the PSS occurs within an initial reaction time of 30 minutes in the composite thin film, and the PSS is concentrated in an upper region adjacent to the upper surface of the composite thin film. After 30 minutes of the initial reaction time, at least a portion of the PSS concentrated in the upper region is removed, and it can be seen that the ratio of the PSS in the lower region adjacent to the lower surface may be higher than that in the upper region.

7 is a view of taking an image for explaining the internal structure of the composite thin film according to an experimental example of the present invention.

Referring to FIG. 7, as described above, (a) of FIG. 7 is a _{top view SEM image of Bi 2} Te ₃ nanowires in the composite thin film, and FIG. 7 (b) is PEDOT:PSS/Bi in the composite thin film. ₂ Te ₃ Nanowires It is a cross-sectional view of the composite thin film structure, and FIG. 7C is a TEM image of _{the Bi 2} Te _{3 nanowires embedded in the PEDOT:PSS matrix in the composite thin film.} 7 (d) to 7 (g) are diagrams for explaining the STEM-EDS mapping of FIG. 7 (c). It can be confirmed that _{the Bi 2} Te ₃ nanowire is embedded as shown in FIG. 7(c).

8 is a graph showing the results of ultraviolet photoelectron spectroscopy (UPS) according to the heat treatment process execution time of the composite thin film according to an experimental example of the present invention.

Referring to FIG. 8 , the UPS was measured while controlling the heat treatment process execution time of the composite thin film according to the above-described experimental example of the present invention to 0 minutes, 10 minutes, 30 minutes, 60 minutes, and 120 minutes. As shown in FIG. 8 , the strength increases while the heat treatment process is performed. According to the experimental example, it can be seen that the Seebeck coefficient has the highest value at 120 minutes among the heat treatment process times of 0 minutes, 10 minutes, 30 minutes, 60 minutes and 120 minutes.

9 is a graph of the PEDOT:PSS work function change in the composite thin film according to the heat treatment process execution time of the composite thin film according to an experimental example of the present invention.

Referring to FIG. 9 , the work function value was measured by performing the UPS. The change of the work function according to the heat treatment process execution time is as shown in the graph, and the gray dot represents the work function value _{of the Bi 2} Te _{3 nanowire.} The ratio of PSS and PEDOT decreases according to the heat treatment process execution time, indicating that the work function value of PEDOT:PSS decreases. The work function value of the Bi ₂ Te ₃ nanowire is a fixed value of 4.83 eV. _{It can be seen that a difference between the Bi 2} Te ₃ nanowire work function and the PEDOT:PSS work function value occurs according to the PEDOT:PSS work function value that changes according to the removal ratio of the PSS.

10 is a standardized S2P XPS graph of a composite thin film according to an experimental example of the present invention.

Referring to FIG. 10 , it was confirmed that the ratio of PSS:PEDOT in the composite thin film decreased according to the heat treatment process time, and the work function value was changed accordingly. There are two peaks in the XPS spectrum. One is located at a high binding energy corresponding to PSS, and the other is located at a low binding energy corresponding to PEDOT. The strength generated in the PSS decreases significantly during the long-running heat treatment process time.

11 is a graph showing the PSS and PEDOT ratios that change according to the heat treatment process execution time of the PEDOT:PSS block copolymer in the composite thin film according to the experimental example of the present invention.

Referring to FIG. 11 , the ratio of the PSS to the PEDOT is shown in a graph according to the time for performing the heat treatment process. According to the heat treatment process performed for a short time, phase separation between the PEDOT and the PSS occurs at 5 minutes of the heat treatment process time, indicating that the concentration of the PSS in the upper region increases. Then, when the heat treatment process is performed on the composite thin film for a long time, the PSS is removed. It can be seen that the PSS removal in the upper region is saturated from 90 minutes of the heat treatment process.

12 is a graph of work function values according to PSS and PEDOT ratios in a composite thin film according to an experimental example of the present invention.

Referring to FIG. 12 , it can be seen that the PEDOT:PSS work function value in the composite thin film changes according to the ratio of the PSS to the PEDOT. It can be seen that the value of the work function increases as the ratio of the PSS increases. It can be seen that the gray dot is a fixed value as the work function value _{of the Bi 2} Te _{3 nanowire.}

13 is a view showing the change of PEDOT:PSS structure and work function value according to the heat treatment process execution time (0 min, 10 min, 120 min) of the composite thin film according to an experimental example of the present invention.

Referring to FIG. 13 , it can be seen that the phase separation occurred at 10 minutes of performing the heat treatment process, and thus PSS was concentrated near the Fermi level. Thereafter, when the PSS of 120 minutes for performing the heat treatment process is confirmed, the PSS near the Fermi level is removed, so that the PSS in the lower region opposite to the vicinity of the Fermi level has a relatively larger amount than the PSS ratio near the Fermi level that can be checked Since the PSS is concentrated in the upper region of the composite thin film, it can be confirmed that the density of states near the Fermi level is reduced.

14 is a graph of the Seebeck coefficient and the energy level difference (barrier energy) value that change according to the execution time of the heat treatment process of the composite thin film measured at room temperature according to an experimental example of the present invention.

Referring to FIG. 14 , when the energy level difference value is less than 0, the Seebeck coefficient is relatively low, but when the energy level difference value is greater than 0, it can be confirmed that the Seebeck coefficient has a relatively large value. It can be seen that the Seebeck coefficient can be increased by optimizing the energy level difference value by adjusting the work function value. In particular, it can be seen that when the energy level difference value is 0.11 eV, the time for performing the heat treatment process having the maximum Seebeck coefficient is 120 minutes.

15 is a schematic band diagram of a composite thin film having an energy barrier and a composite thin film without an energy barrier due to a difference in energy level according to an experimental example of the present invention.

15, the schematic diagram of the top of the PEDOT: PSS Fermi level of the work function value of the Bi ₂ Te ₃ is greater than the work function value of the nanowire, the import valence upward bending of the Bi ₂ Te ₃ nanowires Since no energy barrier is formed, both the carrier with the low energy and the carrier with the high energy are transported to the valence band of _{the Bi 2} Te _{3 nanowire.} On the other hand, the schematic diagram at the bottom shows that when the work function value of the PEDOT:PSS Fermi level _{is smaller than the work function value of the Bi 2} Te ₃ nanowire, the energy barrier is formed. It can be seen that the carriers having the low energy collide with the energy barrier and are selectively dispersed by the Fermi level, and the carriers having the high energy are transported to the valence band _{of the Bi 2} Te _{3 nanowire.}

16 is a graph showing the change in electrical conductivity _{of the PEDOT:PSS/Bi 2} Te ₃ nanowire composite thin film according to the heat treatment process execution time of the composite thin film measured at room temperature according to an experimental example of the present invention.

Referring to FIG. 16 , it can be seen that the electrical conductivity of the composite thin film increases according to the heat treatment time of the composite thin film. The electrical conductivity increases as the heat treatment process duration continues, and it can be seen that the heat treatment process time becomes saturated at 90 minutes. It can be seen that the PSS is substantially removed at 90 minutes and has the highest electrical conductivity value at 120 minutes.

17 is a graph showing changes in the thermoelectric power factor (power factor) _{of the PEDOT:PSS/Bi 2} Te ₃ nanowire composite thin film according to the heat treatment process execution time of the composite thin film measured at room temperature according to an experimental example of the present invention.

Referring to FIG. 17 , it can be seen that the thermoelectric power factor of the composite thin film increases according to the heat treatment process execution time. The thermoelectric power factor is S ² σ, and as the values of the Seebeck coefficient (S) and the electrical conductivity (σ) increase, the value of the thermoelectric power factor d also increases.

18 is a grazing incident wide-angle X-ray (GIWAXS) pattern of a _{PEDOT:PSS/Bi 2} Te ₃ nanowire composite thin film in which the heat treatment process time of the composite thin film according to an experimental example of the present invention is 0, 10, and 120 minutes. .

Referring to FIG. 18 , in order to confirm the effect of the heat treatment process of the composite thin film contributing to the electrical conductivity value, the composite thin film was measured through GIWAXS. Samples of the above measurements were measured at 0 min, 10 min, and 120 min. As shown in FIG. 18 , it can be seen that the PEDOT chain is well connected according to the phase separation of the PEDOT and the removal of the PSS at 10 minutes of the heat treatment process execution time. The strength of the ring pattern significantly decreases between about 60˚ and 120˚ depending on the distribution _{of Bi 2} Te ₃ nanowires in the PEDOT:PSS matrix gradient. The pure PEDOT:PSS thin film also showed a similar scattering pattern without strong diffusion or dispersion from _{the Bi 2} Te _{3 nanowire.}

19 is a graph for showing results according to an experimental example of the present invention.

Referring to FIG. 19 , saturation of PSS removal occurs at 90 minutes of heat treatment process execution time of the composite thin film. Thereafter, an energy barrier is formed by the energy level difference value between the Fermi level of PEDOT:PSS, in which the composite thin film is a block copolymer, and the _{valence band of the Bi 2} Te _{3 nanowire at 120 minutes of the heat treatment process execution time.} Only carriers having high energy are transported to the valence band of _{the Bi 2} Te ₃ nanowire by the formed energy barrier, thereby generating an energy filtering effect. Accordingly, it can be seen that the Seebeck coefficient increases.

As mentioned above, although the present invention has been described in detail using preferred embodiments, the scope of the present invention is not limited to specific embodiments and should be construed according to the appended claims. In addition, those skilled in the art will understand that many modifications and variations are possible without departing from the scope of the present invention.

110: composite thin film
120: block A
130: block B
140: nano wire

Claims (13)

Preparing a block copolymer including block A and block B, and a base source including nanowires;
providing the base source on a substrate to form a composite thin film;
Providing a vapor in which a solvent for selectively removing the block B from the block copolymer is vaporized to the composite thin film, comprising the step of removing at least a portion of the block B in the composite thin film,
While the heat treatment is performed for a reference time, the block A and the block B are separated,
After the reference time, the separated block B is removed, and the density of states near the Fermi level of the block copolymer is reduced.
According to claim 1,
The solvent is a method of manufacturing a composite thin film structure comprising a polar solvent.
3. The method of claim 2,
The polar solvent is DMSO (Dimethyl sulfoxide), EG (Ethylene glycol), DMF (Dimethyl formamide), or MeOH (Methanol) method of manufacturing a composite thin film structure comprising at least one of.
According to claim 1,
While the vapor in which the solvent is vaporized is provided to the composite thin film, a method of manufacturing a composite thin film structure comprising a heat treatment.
5. The method of claim 4,
The energy level difference between the Fermi level of the block copolymer and the valence band of the nanowire is a method of manufacturing a composite thin film structure comprising controlling the heat treatment time.
6. The method of claim 5,
When the heat treatment is performed for 120 minutes, the method of manufacturing a composite thin film structure comprising that the Seebeck coefficient is a maximum value.
6. The method of claim 5,
By the heat treatment time, the removal rate of the block B in the block copolymer is controlled,
According to the removal rate of the block B, the method of manufacturing a composite thin film structure comprising controlling the Seebeck coefficient of the composite thin film.
According to claim 1,
An energy level difference is provided between a Fermi level of the block copolymer and a valence band of the nanowire, an energy barrier is formed,
Carriers having a relatively low energy are selectively prevented from being transported to the valence band of the nanowire by the energy barrier,
A method of manufacturing a composite thin film structure comprising transporting a relatively high energy carrier to a valence band of the nanowire.
Preparing a block copolymer including block A and block B, and a base source including nanowires;
providing the base source on a substrate to form a composite thin film;
A solvent vaporized vapor for selectively removing the block B from the block copolymer is provided to the composite thin film to remove at least a portion of the block B from the composite thin film,
As the block B is removed, the method of manufacturing a composite thin film structure comprising reducing the thickness of the composite thin film.
Board; and
A composite thin film disposed on the substrate and comprising a block copolymer of block A and block B and a nanowire,
An energy level difference is provided between a Fermi level of the block copolymer and a valence band of the nanowire, an energy barrier is formed,
Carriers having a relatively low energy are selectively prevented from being transported to the valence band of the nanowire by the energy barrier,
A composite thin film structure comprising a relatively high energy carrier transported to a valence band of the nanowire.
11. The method of claim 10,
The block A comprises that PEDOT,
Including that the block B is PSS,
The block copolymer includes that of PEDOT: PSS,
The nanowire is a Bi ₂ Te ₃ composite thin film structure comprising a nanowire.
11. The method of claim 10,
The energy level difference is a composite thin film structure comprising that of 0.11 ~ 0.12eV.
11. The method of claim 10,
The composite thin film includes a lower surface adjacent to the substrate and an upper surface opposing the lower surface,
The lower region adjacent to the lower surface of the composite thin film, the composite thin film structure comprising a higher ratio of the block B than the upper region adjacent to the upper surface of the composite thin film.

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