KR101815748B1 - N type thermoelectric element - Google Patents
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Abstract
The present invention provides a thermoelectric device including a polymer film doped with an ionic liquid and being driven by n-type.
Description
BACKGROUND OF THE
Thermoelectric materials that generate electricity using a temperature gradient have received much attention. Many thermoelectric materials based on renewable resources such as waste heat have been explored for a variety of applications, including small heaters / coolers, short-term generators, and human interface devices. The most common thermoelectric materials are composed of inorganic components such as alloys, metallic semiconductors and clathrates, which have excellent thermoelectric performance. However, inorganic thermoelectric materials are limited to high-temperature (400K or more) operation, are rare, expensive, and have very hard properties and are difficult to process. To overcome this problem, many researchers have explored alternative thermoelectric materials such as conductive polymers, organic semiconductors, organic / inorganic composites, inorganic or organic hybrids containing carbon materials.
Among alternative thermoelectric materials, conductive polymers are emerging as a potent substance. Conductive polymers have significant advantages such as simple processability, low cost fabrication, high electrical conductivity, excellent Seebeck coefficient, and ease of composite fabrication with other materials. In particular, polyaniline (PANI) is one of the most popular conductive polymers and has an easily controllable electrical conductivity due to its ability to switch chemical salts and chemical base forms. Therefore, the polymer shape, chemical structure, physical activity, properties of polyaniline, and properties of other materials have been extensively studied.
Untreated polyaniline does not have high electrical conductivity because the electrical state of the polymer is neutral. Typically, acid or self-doped polyaniline materials exhibit hole-transporting properties and therefore behave like p-type thermoelectric elements due to the electron-attracting properties of nitrogen atoms in the polyaniline. To obtain n-type polyaniline materials with electron-transport properties, the researchers attempted to use various dopants such as hydrides, n-type inorganic materials, carbon materials, and self-doping components. It has been reported that the complex of double-walled carbon nanotubes and n-type polyaniline exhibits a thermal power of -21.54 ㎶ · K -1 in the initial boron-doped polyaniline state. It has also been reported that the complex of poly (diallyldimethylammonium chloride) and self-doped carboxylated polyaniline exhibits n-type electrical properties at high pH. The thermoelectric performance of the functionalized CNT / polyaniline complex was reported to show a thermal power of -58 ㎶ · K -1 under controlled conditions. In order to produce soluble n-type materials, there have been also studies on n-doped polyaniline produced using a strong reducing agent. However, unlike acids and self-dopants in conducting polyanilines, n-type dopants are very unstable and readily oxidized in air. There is therefore a considerable demand for the development of strong and stable n-type dopants for polyanilines.
SUMMARY OF THE INVENTION An object of the present invention is to provide a thermoelectric device driven by n-type.
Another object of the present invention is to provide an n-type thermoelectric device having excellent thermoelectric performance and long-term stability under atmospheric conditions.
In order to achieve the above object, the present invention provides a thermoelectric device including a polymer film doped with an ionic liquid and being driven by n-type.
In the present invention, the polymer may be at least one selected from the group consisting of polyaniline, polyacetylene, polypyrrole, polythiophene, polyphenylene, poly (ethylene dioxythiophene), poly (styrenesulfonate) (Phenylene), polyfluorene, poly (arylamine), and the like.
In the present invention, the ionic liquid may be at least one selected from the group consisting of an imidazolium series, a pyridinium series, an ammonium series, a phosphonium series, an oxazolium series, a piperidinium series, a pyrazinium series, a pyrazolium series, a pyridazinium series, a pyrimidinium series, , A pyrrolinium-based, a pyrrole-based, and a triazolium-based cation; And anions selected from the group consisting of sulfates, sulfonates, halides, nitrates, haloborates, halophosphates, and aluminum halides.
In the present invention, the carrier concentration of the polymer film may have a negative value.
In the present invention, the decomposition temperature of the anion in the ionic liquid may be lower than the decomposition temperature of the cation.
In the present invention, the concentration of the anion in the polymer film is lower than the cation, and the polymer may partially negatively charge the polymer.
In the present invention, the work function of the polymer film can be lowered after doping as compared with that before doping.
Electrical conductivity of the polymer film in the present invention is 0.01 to 10 S · m -1, the Seebeck coefficient is an absolute value of 10 to 900 ㎶ · K -1, the carrier concentration is as an
In the present invention, the electrical conductivity and the Seebeck coefficient of the polymer film can be maintained at 100% of the average value for 1 to 100 days at atmospheric conditions.
In the present invention, the polymer film may have a thickness of 100 to 2000 nm and an area of 0.1 to 10
The present invention also relates to a method for preparing a semiconductor device, comprising the steps of: doping a polymer with an ionic liquid; Forming a polymer doped with an ionic liquid into a film; And a step of annealing the polymer film.
In the present invention, the annealing temperature may be higher than the decomposition temperature of the anions in the ionic liquid.
In the present invention, the anion in the ionic liquid can be at least partially decomposed through annealing.
The thermoelectric device according to the present invention can be driven into n-type by including a polymer doped with a specific ionic liquid, has excellent thermoelectric performance, and can have long-term stability under atmospheric conditions.
Figure 1 shows the chemical structure of n-type polyaniline (PANI-IL) doped with 1-ethyl-3-methylimidazolium ethylsulfate.
Figure 2 shows the ATR-FTIR spectrum of polyaniline (PANI), ionic liquid (IL), and n-type polyaniline-ionic liquid (PANI-IL).
3 shows an SEM image of an n-type polyaniline-ionic liquid film (PANI-IL).
Figure 4 shows the RAMAN spectrum of polyaniline (PANI) and n-type polyaniline-ionic liquid (PANI-IL).
Figure 5 shows the UV-Vis-NIR spectra of polyaniline (PANI) and n-type polyaniline-ionic liquid film (PANI-IL).
Figure 6 shows the UPS spectrum of polyaniline (PANI) and n-type polyaniline-ionic liquid (PANI-IL).
7A is a schematic view of a thermoelectric measurement setup and a polyaniline-ionic liquid (PANI-IL) film coated on glass, and FIG. 7B is a graph showing the conductivity of an ionic liquid doped n-type polyaniline , Seebeck coefficient, and stability data.
8 shows data measured by a Hall effect measuring apparatus.
Hereinafter, the present invention will be described in detail.
BACKGROUND OF THE
The thermoelectric device according to the present invention includes a polymer film doped with an ionic liquid and is driven by n-type. For example, when a temperature gradient is formed at both ends of a polymer film, electrons and / or ions may move to a circuit connected to the polymer film.
Generally, n-type materials by electron transfer are low in electron mobility, and electrons are easily trapped by oxygen or moisture when electrons are injected in a driving environment. Therefore, it is slower than p-type Has come.
However, a bipolar circuit for constituting various circuits such as a bipolar transistor, a conversion device, and the like is required to be developed so as to have low power consumption and fast switching speed.
Until now, thermoelectric devices driven by n-type polymers did not even know which laboratory is driven by n-type, nor did they identify mechanisms and stability. In the present invention, a thermoelectric device driven by an n-type polymer was first developed, and the mechanism and stability of a thermoelectric device driven by an n-type polymer were also confirmed.
The polymer used in the present invention may be a conductive polymer and may be, for example, polyaniline, polyacetylene, polypyrrole, polythiophene, polyphenylene, poly (ethylene dioxythiophene) Sulfide), polysulfone, poly (vinylene phenylene), polyfluorene, poly (arylamine), and preferably polyaniline. As the polyaniline, a polyaniline emeraldine base can be used. The polyaniline exhibits p-type characteristics, but when doped with an environmentally friendly ionic liquid according to the present invention, it can exhibit n-type characteristics that are stably driven in air and have high charge mobility.
In the present invention, an ionic liquid can be used as a chemical dopant for imparting n-type characteristics to a polymer. An ionic liquid is an ionic salt present as a liquid at a temperature of 100 ° C or lower, and an ionic liquid present as a liquid at room temperature is called an ionic liquid at room temperature. Ionic liquids are low melting points, nonvolatile, non-toxic, non-flammable, and have excellent thermal stability and ionic conductivity. Ionic liquids can consist of organic cations and anions.
Examples of the cation include imidazolium, pyridinium, ammonium, phosphonium, oxazolium, piperidinium, pyrazinium, pyrazolium, pyridazinium, pyrimidinium, pyrrolidinium, Ethyl-3-methylimidazolium (emim), 1-n-butyl-3-methylimidazolium (bmim), 1-n- Methylimidazolium (hmim), 1- (3'-phenylpropyl) -3-methylimidazolium (ppmim) and 1-butylpyridinium (bp) The azolium-based cation may be used.
Examples of the anion include sulfate, sulfonate, halide, nitrate, haloborate, halophosphate, and aluminum halide, and examples thereof include methyl sulfate, ethyl sulfate, butyl sulfate, octyl sulfate, ethylene glycol monomethyl ether sulfate, polyethylene glycol -5 Kokomo titanium methosulfate, F -, Cl -, Br -, I -, NO 3 -, BF 4 -, PF 6 -, AlCl 4 -,
Preferably, in the present invention, the ionic liquid may include an imidazolium-based cation and a sulfate-based anion, and more preferably, 1-ethyl-3-methylimidazolium ethylsulfate may be used as an ionic liquid.
In the present invention, the carrier concentration of the polymer film may have a negative value. This can be a conclusive evidence that the thermoelectric element according to the present invention is driven to n-type. When driven in p-type, the carrier concentration can have a positive value. The carrier concentration can be measured using a Hall effect measuring device or the like.
In the present invention, the decomposition temperature of the anion in the ionic liquid may be lower than the decomposition temperature of the cation. The decomposition temperature of the anion may be, for example, 90 to 150 캜, preferably 100 to 140 캜, more preferably 110 to 130 캜. The decomposition temperature of the cation may be, for example, 240 to 310 ° C, preferably 250 to 300 ° C, more preferably 260 to 290 ° C.
The concentration of anions in the polymer film according to the present invention may be lower than the cation. By at least partially decomposing the anion through annealing at a temperature higher than the decomposition temperature of the anion in the ionic liquid, the concentration of the anion in the polymer film can be lowered relative to the cation, and by the cation having a relatively high concentration, A negative charge can be generated, and thus an n-type polymer thermoelectric device can be manufactured.
For example, when an ionic liquid in which an ethyl sulfate anion and a 1-ethyl-3-methyl imidazolium cation exist together is added to polyaniline in the form of an emeraldine base, The proton (H) of the proton (H) may be removed to form a deprotonated polyaniline structure, whereby an n-type polyaniline can be prepared.
The decomposition temperature (T d ) of the ethylsulfate, anion of the ionic liquid, can start from about 120 ° C, and the T d of the cation 1-ethyl-3-methylimidazolium can start from about 275 ° C. Accordingly, in the filming step of the polyaniline doped with the ionic liquid, the number of the anions is drastically reduced through the heat treatment at 150 ° C for 10 minutes, the N atoms of the polyaniline are partially negatively charged by the remaining cations, Can be produced.
The work function of the polymer film according to the present invention can be lowered after doping as compared with that before doping, and thus the polymer film doped with the ionic liquid can exhibit n-type semiconductor behavior. The work function of the polymer film may be lowered by 1 to 50%, preferably 3 to 30%, more preferably 5 to 20% after doping based on the pre-doping. The work function of the polymer film doped with the ionic liquid may be, for example, 4 to 4.8 eV, preferably 4.1 to 4.7 eV, more preferably 4.2 to 4.6 eV.
The electrical conductivity of the polymer film according to the present invention may be 0.01 to 10 S m -1 , preferably 0.05 to 5 S m -1 , more preferably 0.1 to 1 S m -1 .
The absolute value of the Seebeck coefficient of the polymer film according to the present invention may be 10 to 900 ㎶ · K -1 , preferably 50 to 500 ㎶ · K -1 , more preferably 100 to 200 ㎶ · K -1 .
The carrier concentration of the polymer film according to the present invention is 1 × 10 13 to 9 × 10 15 cm -3 , preferably 5 × 10 13 to 5 × 10 15 cm -3 , more preferably 1 × 10 14 cm -3 , To 1 x 10 < 15 > cm < -3 >.
The carrier mobility of the polymer film according to the present invention is in the range of 1 × 10 -1 to 9 × 10 1
The polymer film according to the present invention can have long-term stability under atmospheric conditions. For example, the electrical conductivity and the Seebeck coefficient of a polymer film is ± 80% of the mean value for ± 1% of the mean value for 1 to 100 days, preferably 5 to 50 days, and more preferably 10 To < / RTI > 60% of the mean value for 20 to 20 days.
The thickness of the polymer film according to the present invention may be 100 to 2000 nm, preferably 200 to 1000 nm, more preferably 300 to 500 nm. If the thickness is too thin, the electrical conductivity and thermoelectric performance may be deteriorated.
The area of the polymer film according to the present invention may be 0.1 to 10
The polymer film in the thermoelectric device according to the present invention can be formed on a substrate. As the substrate, a glass substrate, a plastic substrate, or the like can be used. A hot source and a cold source for forming a temperature gradient in the polymer film may be installed in the lower part of the substrate, and a Peltier element may be used as a hot source and a cold source. The Peltier element can be attached to the heat sink to avoid thermal disturbances and maintain a controlled temperature gradient. The polymer film may be provided with a plurality of probes for measuring voltage and current, and a plurality of thermocouples for temperature measurement may be provided. In addition, a circuit can be connected so that current flows through the polymer film.
The present invention also relates to a method for preparing a semiconductor device, comprising the steps of: doping a polymer with an ionic liquid; Forming a polymer doped with an ionic liquid into a film; And a step of annealing the polymer film.
In the doping step, the polymer and the ionic liquid are mixed. The mixing ratio of the polymer and the ionic liquid may be, for example, 0.01 to 1 g, preferably 0.05 to 0.5 g, of the polymer based on 1 mL of the ionic liquid. The polymer may be first dissolved in a solvent and then mixed with an ionic liquid. As the solvent, m-cresol or the like can be used. The concentration of the polymer in the solvent may be, for example, 0.001 to 0.1 g / mL, preferably 0.005 to 0.05 g / mL. The mixing can be effected under suitable stirring, and the mixing time can be, for example, from 1 hour to 2 weeks.
In the film forming step, a mixture of a polymer and an ionic liquid may be coated or deposited on a substrate to form a film. The substrate may be washed with acetone, DI water, methanol or the like prior to coating or deposition. In addition, the substrate can be treated with oxygen plasma to increase the adhesion between the substrate surface and the polymer. As the coating and deposition methods, drop casting, spin coating and the like can be used.
In the annealing step, heat treatment can be performed at a temperature higher than the decomposition temperature of the anion in the ionic liquid. The anion in the ionic liquid can be at least partially decomposed through annealing. The annealing temperature may be, for example, 100 to 200 占 폚, preferably 120 to 180 占 폚, and more preferably 140 to 160 占 폚. The annealing time may be, for example, 5 to 60 minutes, preferably 10 to 50 minutes, more preferably 20 to 40 minutes.
[Example]
1. Material
Aniline monomer (C 6 H 5 NH 2, ≥ 99.5%), ammonium persulfate ((NH 4) 2 S 2 O 8, ≥ 98.0%), hydrochloric acid (HCl, 37%), aqueous ammonium hydroxide (NH 4 OH, 28.0 to 30.0%) and m-cresol (CH 3 C 6 H 4 OH, 99%) were obtained from Sigma-Aldrich Co. LLC. These reagents were used without further purification. Ionic Liquid 1-Ethyl-3-methylimidazolium ethyl sulfate (C 8 H 16 N 2 O 4 S, ≥95%) was used as a chemical dopant and was also obtained from Sigma-Aldrich Co. LLC, and subjected to vacuum distillation treatment. All other solvents and chemicals were used as supplied.
2. Synthesis of polyaniline emeraldine base
Ammonium persulfate (APS, 23 g) and aniline monomer (40 mL) were dissolved in 400 mL and 600 mL of 1 M HCl, respectively, to synthesize polyaniline through chemical oxidation polymerization. After cooling the dispersion to 276-280 K, the dispersion of APS in HCl was slowly added to the aniline / HCl dispersion with stirring. Polymerization of the polyaniline was carried out with cooling for 5 hours, after which the polyaniline was precipitated from the solution over 1 hour. The polymer was washed with 1 M HCl and deionized (DI) water and vacuum filtration. The color of the polyaniline was light green. Since the product in 0.1 M NH 4 OH (250 mL ) was re-dissolved overnight. The suspension was then filtered and the collected product was washed repeatedly with DI water. Finally, the polymer was dried in a vacuum oven for 24 hours. At this point, the polyaniline emeraldine base was dark blue.
3. Preparation of 1-ethyl-3-methylimidazolium ethylsulfate doped polyaniline (PANI-IL) film
After dark blue polyaniline (0.2 g) was dissolved in m-cresol (10 mL), 1-ethyl-3-methylimidazolium ethylsulfate (2 mL) was slowly added to this solution. The polyaniline / ionic liquid / m-cresol mixture was stirred at a constant rate for one week and the color gradually changed from blue to green. Prior to the deposition of a conductive ionic liquid-doped polyaniline (PANI-IL) film, a 10 mm x 10 mm glass substrate was washed with acetone, DI water and methanol for 10 minutes each in this order to remove glass impurities, Gt; 1 hour < / RTI > in an oven. Thereafter, the glass substrate was treated with an oxygen plasma for 5 minutes to increase the adhesion between the glass surface and the polymer. The prepared PANI-IL material was filtered using a syringe filter (PTFE membrane having a pore size of 5.0 mu m) and then deposited on a glass substrate through drop casting of 70 mu l from a micropipette. Finally, the PANI-IL film on the glass substrate was annealed at 150 DEG C for 30 minutes.
4. Measurement of thermoelectric properties
A self-fabricating device was used to measure the thermoelectric properties (TE) of doped polyaniline films, including electrical conductivity and Seebeck coefficient. The device consists of four gold probes, two Peltier devices, a thermocouple, a source / meter and a voltage and current system. The Peltier device was attached to an aluminum heat sink and provided an appropriate temperature gradient. The current / voltage was controlled using a Keithley 2400 source / meter and provided a starting temperature gradient of 10 ° C. Electrical conductivity was calculated from the surface resistance measured using film thickness (confirmed using
5. Results and Discussion
As a conductive polymer, PANI was synthesized by oxidation polymerization using an organic solvent (eg, m-cresol) using ammonium persulfate (APS). The chemical structure of the prepared polyaniline was that of emeraldine base, so the conductivity of the polymer could be controlled by dopant addition. Depending on the choice of dopant type (e.g., an oxidizing or reducing agent), the polyaniline can operate as an n-type or p-type conductive material, respectively. In order to obtain an n-type conductive material, polyaniline should be doped using a strong reducing agent such as a metal hydride. However, metal hydride reducing agents are readily oxidizable and therefore extremely unstable when exposed to moisture. Therefore, polyaniline doped with a hydride reducing agent is difficult to maintain n-type characteristics. Ionic liquids, which are salts composed of both anions and cations, are stable charge pairs at atmospheric conditions. Figure 1 shows n-type polyaniline doped with 1-ethyl-3-methylimidazolium ethylsulfate. The ionic liquid has a high decomposition temperature and excellent thermal stability under atmospheric conditions. When doped with an ionic liquid, the chemical structure of the polyaniline in the emeraldine base form changed due to the presence of anions and cations in the ionic liquid to produce charged potentials. As a result, ionic liquid-doped polyaniline (PANI-IL) exhibited electrical conductivity. In addition, PANI-IL was stable at atmospheric conditions and functioned as a thermoelectric material.
The chemical structure of polyaniline (PANI), 1-ethyl-3-methylimidazolium ethylsulfate, and PANI-IL was measured using Fourier transform infrared (FT-IR) spectroscopy as shown in FIG. Spectra were obtained over the range of 1800 cm -1 to 400 cm -1 . Peaks due to the C = C stretching mode of the aromatic rings of PANI and PANI-IL were observed at 1564 cm -1 and 1484 cm -1 , respectively. The CN stretching modes at 1310 cm -1 and 1180 cm -1 for PANI and PANI-IL were attributed to the benzoid and quinoid structures, respectively. The peak at 810 cm -1 was due to the CH stretching of the aromatic rings of PANI and PANI-IL. FT-IR peaks for the 1-ethyl-3-methylimidazolium cations in the ionic liquid were observed at 1574 cm -1 and 1169 cm -1 , indicating that the in-plane CN stretching mode and in-plane CC, N-CH 2 , and N-CH 3 CN stretching modes, respectively. The peaks for the anion component of the ionic liquid were observed at 1215 cm -1 , 1014 cm -1 and 912 cm -1 , corresponding to the CO-SO 3 symmetric and asymmetric stretching modes. After annealing the PANI-IL film, peaks for anions disappeared in the FT-IR spectrum of the polymer due to partial degradation of the ethylsulfate molecules. This result implies that the conductive PANI-IL film exhibits the necessary structure for an organic thermoelectric material having n-type characteristics.
The scanning electron microscope (SEM) image of Figure 3 shows the surface morphology of the PANI-IL film. Uneven patterns could be seen on the surface of the conductive PANI-IL, all of which were formed in a single direction on the glass substrate. Thus, the surface structure of the PANI-IL film was constructed in a form suitable for charge transport.
Next, the Raman spectra of the PANI and PANI-IL films were analyzed to evaluate the effect of the ionic liquid, and the results are shown in FIG. The chemical structure of the conductive material has a significant effect on the strength of the Raman peak. Thus, in the spectrum of the PANI film, the peak for the C = N stretching vibration mode of the quinoid diimine structure appeared at 1485 cm -1 . On the other hand, in the Raman spectrum of the PANI-IL film, this peak was not observed due to the doping state of the PANI structure due to the addition of the ionic liquid. The peak at 1608 cm -1 of the PANI-IL spectrum was associated with the CC benzoid structure. In addition, a peak at 1235 cm -1 corresponding to the CN bond vibration of the benzodiazide group was also observed. This peak was attributed to the ionic liquid-doped polyaniline structure. Also, the Raman peak at 1159 cm -1 of the PANI spectrum was changed to 1171 cm -1 in the PANI-IL spectrum due to the presence of the benzoid mode in the doped state. Also, as a result of this shift, the CN stretching peak due to doping appeared at 1339 cm -1 in the spectrum of the PANI-IL film. The results also indicate that the PANI-IL film is an n-type thermoelectric material and exhibits conductivity characteristics in the doped state.
In order to further confirm the chemical structure of the undoped PANI state and the n-type doped PANI-IL state, the ultraviolet-visible-near-infrared (UV-vis-NIR) spectrum shown in FIG. 5 was obtained. The absorption peaks of the undoped PANI appeared at 320 and 620 nm, respectively, due to the transition state of the benzoid structure and the exciton absorption from the benzoid state to the quinoid state. Absorption peaks for doped PANI-IL appeared around 400 and 800 nm, corresponding to π-π * electron transition and π-polaron excitation states. In addition, the intensity of the 320 and 620 nm peaks observed in the undoped PANI spectra was slightly reduced in PANI-IL. The absorption peak for the doping polymer indicates that PANI-IL is composed of an effective carrier-transfer structure and is electrically n-type conducting polymer.
In addition, in order to demonstrate the n-type doping state of the polyaniline-ionic liquid film, an undoped PANI coated on ITO glass and an n-type doping (ITO) coated with ultraviolet photoelectron spectroscopy (UPS) equipped with a He I source (21.22 eV) The work function of PANI-IL was analyzed. The work function was calculated by the following equation.
φ = hv - | E cutoff - E F |
Here, φ, hv, E cutoff , and E F are work function, photon energy, kinetic energy cutoff, and Fermi energy, respectively. The UPS spectrum of PANI and PANI-IL is shown in Fig. As shown in this figure, the Fermi energy of the PANI and PANI-IL films were all considered to be zero. Kinetic energy cut-off of the initial PANI and the n-type IL-PANI film (E cutoff) were respectively 16.39 and 16.68 eV. According to the above equation, the work function of PANI was obtained at 4.83 eV. The n-type PANI-IL work function was changed to 4.54 eV, slightly lower than the initial polyaniline film. As a result, the ionic liquid doped polyaniline (PANI-IL) film exhibited n-type semiconductor behavior.
Next, in order to evaluate the thermoelectric properties of the organic n-type PANI-IL film, an analytical instrument for measuring thermoelectric properties of a polymer film using Peltier element for PANI-IL film was developed as shown in FIG. The n-type PANI-IL film was coated by drop casting onto a pre-cleaned glass substrate using O 2 plasma. Then, the PANI-IL film was baked to 150 ° C for 30 minutes to evaporate the residual solvent and decompose the sulfonate group of the anion portion of PANI-IL. This annealing process induced selective removal of the negatively charged ethyl sulfate groups instead of disappearance of the imidazolium group from the PANI-IL film. This phenomenon was due to the different thermal stability of the ethylsulfate and imidazolium groups in ionic liquids. Decomposition of ethyl sulfate takes place at 120 ° C, whereas decomposition of imidazolium takes place at 275 ° C. Upon removal of the ethyl sulfate groups, large amounts of imidazolium cations remained, resulting in charge imbalance in the PANI-IL film. To cope with this unstable charge imbalance, the PANI polymer provided a negative charge. Thus, PANI-IL was assumed to be positively charged, with doped electrical properties, in other words n-type thermoelectric material. Table 1 summarizes the electrical properties and thermoelectric performance of PANI-IL. In Table 1, the Seebeck coefficient represents the average value.
Untreated PANI films did not exhibit electrical properties or thermoelectric performance. The electrical conductivity of PANI-IL was measured to be 0.23 S · m -1 , which was lower than that of p-type PANI emeraldine because PANI-IL was in the quasi-doped state and completely doped p-type PANI material Because it is an unstable compound. As a result, the PANI-IL film showed a low charge carrier concentration of 2.262 × 10 14 cm -3 . On the other hand, the PANI-IL material showed an excellent charge carrier mobility of 2.492 × 10 0 ㎠ · V -1 s -1 , which is higher than that of other doped PANI polymers. In addition, the carrier mobility of PANI-IL was much higher than other materials such as pentacene, PCBM, and perylene derivatives. Considering the high carrier mobility and low carrier concentration after annealing, the PANI-IL film also had a very high n-type Seebeck coefficient of mean -138.8 ㎶ · K -1 . The power factor and the thermal conductivity of the n-type PANI-IL material measured by the laser flash device (LFA) method were 4.43 × 10 -3 Ω · m -1 K -2 and 0.22 W · m -1 K -1 . Due to this excellent thermoelectric property, the figure of merit (ZT) of the ionic liquid-doped polyaniline film was 6.04 × 10 -6 , which is a relatively high value for the n-type organic thermoelectric material. Further, the thermoelectric performance of the PANI-IL film was very stable at atmospheric conditions as shown in FIG. 7B. The thermoelectric properties and electrical conductivity of the n-type PANI-IL films did not change over 15 days in the thermoelectric set-up box. Thus, PANI-IL films prepared using imidazolium-based ionic liquids as strong dopants exhibited durable n-type thermoelectric performance at atmospheric conditions.
FIG. 8 shows data measured by the Hall effect measuring apparatus, where the sign of the carrier concentration value is - electron density when the sign of the carrier concentration is negative, and the hole density of + backwardness. Although the p-type thermoelectric element exhibits a positive value of carrier concentration, the n-type thermoelectric element according to the present invention exhibits a negative value of the carrier concentration as shown in Fig. This is the conclusive evidence that the thermoelectric device according to the present invention is driven to n-type. In addition, higher carrier mobility values have higher charge mobility, and the n-type thermoelectric device according to the present invention exhibits high carrier mobility. Thus, the n-type polyaniline-ionic liquid thermoelectric device according to the present invention had high charge mobility as an n-type in which electrons migrate.
Claims (13)
n-type,
The carrier concentration of the polymer film has a negative value,
The decomposition temperature of the anion in the ionic liquid is lower than the decomposition temperature of the cation,
Wherein the concentration of the anion in the polymer film is lower than the cation, and the polymer has a partial negative charge by the cation.
The polymer may be selected from the group consisting of polyaniline, polyacetylene, polypyrrole, polythiophene, polyphenylene, poly (ethylene dioxythiophene), poly (styrene sulfonate), poly (perylene sulphide), polysulfone, poly Polyfluorene, poly (arylamine), and the like.
The ionic liquid may be at least one selected from the group consisting of imidazolium, pyridinium, ammonium, phosphonium, oxazolium, piperidinium, pyrazinium, Cations selected from the group consisting of ammonium, pyrrole, and triazolium; And
Wherein the anion is selected from the group consisting of a sulfate, a sulfonate, a halogen ion, a nitrate, a haloborate, a halophosphate, and an aluminum halide.
Wherein the work function of the polymer film is lowered after doping as compared with that before doping.
The polymer film has an electric conductivity of 0.01 to 10 S · m -1 , an absolute value of a Seebeck coefficient of 10 to 900 ㎶ · K -1 , an absolute value of carrier concentration of 1 × 10 13 to 9 × 10 15 cm -3 , And the mobility is 1 × 10 -1 to 9 × 10 1 cm 2 · V -1 s -1 .
Wherein the electrical conductivity and the Seebeck coefficient of the polymer film are maintained at 100% of the average value for 1 to 100 days at atmospheric conditions.
Wherein the polymer film has a thickness of 100 to 2000 nm and an area of 0.1 to 10 cm 2.
Doping the polymer with an ionic liquid;
Forming a polymer doped with an ionic liquid into a film;
And annealing the polymer film.
Wherein the annealing temperature is higher than the decomposition temperature of the anion in the ionic liquid.
And partially decomposing the anion in the ionic liquid through annealing.
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| KR102324383B1 (en) * | 2018-12-10 | 2021-11-11 | 연세대학교 산학협력단 | Ionic thermoelectric materials and ionic thermoelectric devices comprising the same |
| CN110197869B (en) * | 2019-04-29 | 2021-11-09 | 哈尔滨工业大学（深圳） | Preparation method of polyion liquid-based thermoelectric material |
| US11637231B2 (en) | 2019-10-18 | 2023-04-25 | Kookmin University Industry Academy Cooperation Foundation | Organic thermoelectric material and thermoelectric generator including the same |
| KR102386935B1 (en) * | 2019-10-18 | 2022-04-15 | 국민대학교산학협력단 | organic thermoelectric material and thermoelectric generator having the same |
| CN113178515B (en) * | 2021-04-26 | 2022-11-01 | 重庆大学 | Hydrogel thermoelectric material based on ionic liquid and preparation method thereof |
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