A highly dispersed organic-inorganic composite flexible thermoelectric material and its preparation method

Abstract

This invention relates to a highly dispersed organic-inorganic composite flexible thermoelectric material and its preparation method. The preparation method of the highly dispersed organic-inorganic composite flexible thermoelectric material includes: (1) adding carbon nanotubes to a solution of conjugated polymer A for dispersion, centrifugation and collection of supernatant, then cooling or evaporating and concentrating the supernatant to precipitate solid, filtering, and washing to remove the outer layer of conjugated polymer A that is not bound to the carbon nanotubes by intermolecular forces, to obtain highly dispersed carbon nanotubes coated with a molecular layer thickness of conjugated polymer A; (2) mixing the highly dispersed carbon nanotubes coated with a molecular layer thickness of conjugated polymer A with a solution of conductive polymer B to form a film-forming solution and forming a film to obtain an organic-inorganic composite flexible thermoelectric film, then immersing the organic-inorganic composite flexible thermoelectric film in a doping solution to obtain the highly dispersed organic-inorganic composite flexible thermoelectric material.

Description

Technical Field

[0001] This invention belongs to the field of flexible thermoelectric material preparation technology, specifically relating to a highly dispersed organic-inorganic composite flexible thermoelectric material and its preparation method. Background Technology

[0002] Thermoelectric conversion technology utilizes the Seebeck and Peltier effects of semiconductor materials to directly convert heat energy into electrical energy. As a novel clean energy technology, thermoelectric conversion has been developed and utilized in fields such as the utilization of industrial waste heat and solar thermal power generation. The thermoelectric properties of thermoelectric materials are generally evaluated using the dimensionless thermoelectric figure of merit ZT, where ZT = α. 2 σT / κ, where α is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the absolute temperature.

[0003] Flexible thermoelectric materials and devices can directly convert heat from the human body or environment into electrical energy, and are expected to be applied in fields such as next-generation intelligent micro-nano electronic systems represented by distributed, wearable, and implantable devices. Compared with traditional brittle and rigid thermoelectric materials, flexible thermoelectric materials have the following significant advantages: (1) Good flexibility allows them to make close contact with any geometric shape of the heat source surface, such as the human body, curved pipes, or flexible electronic devices, thereby minimizing contact heat loss and achieving efficient energy conversion; (2) Lightweight, as independent thin-film thermoelectric materials can be firmly attached to various flexible substrates such as the human body and clothing, enabling more applications. In recent years, with the development of flexible electronics technology and the increasing demand for sustainable and multi-purpose energy harvesting, flexible thermoelectric materials have attracted more and more research interest.

[0004] Traditional inorganic semiconductors and half-metals possess extremely high thermoelectric conversion performance, but most are brittle, making it difficult to meet the mechanical performance requirements of flexible thermoelectric materials. Organic materials, on the other hand, exhibit excellent flexibility and low thermal conductivity, but often have poor electrical transport properties, 1-2 orders of magnitude lower than classic inorganic materials. Based on the complementary mechanical, thermal, and electrical properties of organic and inorganic materials, it is hoped that high-performance organic-inorganic thermoelectric composite materials can be developed, thus holding significant research importance.

[0005] In organic-inorganic thermoelectric composites, inorganic materials must be interconnected with organic materials to maintain material integrity and stability. Furthermore, carrier conduction channels must be formed to achieve rapid carrier transport and excellent electrical properties. Since the molecular chains of organic materials are one-dimensional, one-dimensional materials composited with polymers (such as nanowires and whiskers) are the preferred materials for designing and preparing organic-inorganic thermoelectric composites. Single-walled carbon nanotubes (SUVs) are widely used in the preparation of organic-inorganic thermoelectric composites to optimize and control their thermoelectric properties due to their unique one-dimensional structure and excellent electron transport properties. However, to obtain high-performance composites, a large amount of carbon nanotubes is often required. With increasing carbon nanotube content, carbon nanotubes tend to aggregate in the polymer matrix, making them difficult to disperse effectively. This hinders effective interfacial contact between carbon nanotubes and the polymer and increases the thermal conductivity of the composite, thus limiting the potential for performance improvement. How to further improve the dispersibility of carbon nanotubes in the polymer matrix and thus enhance interfacial interactions is a key problem that urgently needs to be solved to improve the thermoelectric performance of organic / inorganic composites.

[0006] To effectively address the dispersion difficulties encountered by carbon nanotubes (CNTs) in applications, two different methods are generally employed: covalent and non-covalent functionalization, to prevent aggregation and thus enhance dispersibility. However, covalent functionalization, based on the covalent bonds of functional groups on the carbon support, disrupts the sp2 hybrid network structure of CNTs, weakening their other superior properties. In contrast, non-covalent methods adsorb surfactants and polymers onto the CNT surface to improve dispersibility. This modification method can significantly reduce aggregation caused by electrostatic repulsion and steric hindrance without damaging the surface structure of the CNTs. Therefore, in recent decades, various surfactants have been developed to improve the dispersibility of CNTs, such as sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and hexadecyltrimethylammonium bromide. However, while these dispersants can improve the dispersibility of CNTs to some extent, they are electrically insulating small molecules that can deteriorate the electrical transport properties of CNTs. Summary of the Invention

[0007] To address the technical problem of carbon nanotubes easily agglomerating in the aforementioned thermoelectric materials, the present invention aims to provide a method for improving the dispersibility of carbon nanotubes while maintaining or improving their electrical transport properties, so as to obtain high-performance organic-inorganic composite flexible thermoelectric materials.

[0008] In a first aspect, the present invention provides a method for preparing a highly dispersed organic-inorganic composite flexible thermoelectric material, comprising: (1) Carbon nanotubes are added to a solution of conjugated polymer A for dispersion, centrifugation and collection of supernatant. Then the supernatant is cooled or evaporated and concentrated to precipitate solid. The solid is filtered and washed to remove the outer layer of conjugated polymer A that is not bound to the carbon nanotubes by intermolecular forces, so as to obtain highly dispersed carbon nanotubes coated with conjugated polymer A with a molecular layer thickness. (2) The highly dispersed carbon nanotubes of the coating molecular layer thickness conjugated polymer A are mixed with the solution of conductive polymer B to form a film-forming solution and a film is formed to obtain an organic-inorganic composite flexible thermoelectric film. Then the organic-inorganic composite flexible thermoelectric film is immersed in a doping solution to obtain the highly dispersed organic-inorganic composite flexible thermoelectric material.

[0009] Preferably, the carbon nanotubes are single-walled carbon nanotubes with a diameter of 0.5–2 nm and a length of 20–30 nm. The conjugated polymer A is an alkyl-substituted conjugated polymer with a molecular weight of 30,000-80,000, preferably polyalkylthiophene or polyalkylselenophene, and more preferably one of butyl-substituted polythiophene, hexyl-substituted polythiophene, octyl-substituted polythiophene, octyl-substituted polyselenophene, dodecyl-substituted polythiophene, and dodecyl-substituted polyselenophene.

[0010] Preferably, the mass ratio of the conjugated polymer A to carbon nanotubes is 1:4 to 4:1, and more preferably 2:1.

[0011] Preferably, the dispersion method is pulsed ultrasonic dispersion; wherein the pulse power is 100-1000w, the pulse temperature is 20-80℃, and the pulse time is 10-60min; The centrifugation is carried out using high-speed centrifugation; wherein the high-speed centrifugation speed is 6000-15000 rpm and the centrifugation time is 10-60 min.

[0012] Preferably, washing is performed using a solvent at 20-70°C; the mass ratio of the coated molecular layer thickness conjugated polymer A to the mass of the highly dispersed carbon nanotubes coated molecular layer thickness conjugated polymer A is controlled to be <5%; the molecular layer thickness ranges from 0.2-2 nm.

[0013] Preferably, the conductive polymer B is at least one of polyaniline, polybenzofuranone, pyrrolopyrrole dione-based conductive polymer, and thiophene-based conductive polymer with a molecular weight of 30,000-100,000; more preferably, the thiophene-based conductive polymer is poly(3,4-dioxothiophene) or poly(3-hexylthiophene).

[0014] Preferably, the mass ratio of the highly dispersed carbon nanotubes of the coating molecular layer thickness conjugated polymer A to the conductive polymer B is 1:4 to 4:1.

[0015] Preferably, the film formation method is drop coating or spin coating, the film formation solvent is toluene, o-xylene, chloroform or tetrahydrofuran, the film formation temperature is 20-60℃, and the film formation time is 0.1-12h.

[0016] Preferably, the doping solution is an iron salt solution, preferably a ferric chloride or bis(trifluoromethanesulfonyl)imide iron solution, the concentration of the iron salt solution is 0.1-1 mol / L, the solvent of the iron salt solution is nitromethane; the immersion time in the doping solution is 0.1-4 h; and the temperature of the doping solution is 20-40 °C.

[0017] Secondly, the present invention provides a highly dispersed organic-inorganic composite flexible thermoelectric material obtained according to the above preparation method.

[0018] Beneficial effects The preparation method provided by this invention utilizes the intermolecular forces between carbon nanotubes and conjugated polymers to form supramolecular self-assembly between carbon nanotubes and conjugated polymers, thereby achieving the unbinding of carbon nanotubes, greatly improving the dispersion of carbon nanotubes and maintaining or enhancing their electrical transport properties. At the same time, the conjugated polymer-coated carbon nanotubes can be composited with a variety of typical conductive polymers. The resulting highly dispersed composite thermoelectric film has good carbon nanotube dispersion and a uniform and continuous film surface, which can significantly improve thermoelectric performance. The process conditions used in this invention are simple, highly controllable, highly repeatable, and have low production costs, which greatly expands the scope of practical applications for carbon nanotube composite polymer thermoelectric materials. Attached Figure Description

[0019] Figure 1 This is a transmission electron microscope (TEM) image of carbon nanotubes coated with conjugated polymer A in Example 1 of this invention. Figure 2 These are atomic force microscopy images of carbon nanotubes before supramolecular assembly and dispersion (a) and after supramolecular assembly and dispersion (b) in Example 1 of the present invention. Figure 3 This is a schematic diagram of the thermoelectric properties of the polythiophene / carbon nanotube composite film (a) obtained without supramolecular assembly and dispersion in Example 1 of the present invention and the polythiophene / polymer-coated carbon nanotube composite film (b) obtained after supramolecular assembly and dispersion. Detailed Implementation

[0020] The present invention is further illustrated by the embodiments described below. It should be understood that the embodiments described below are for illustrative purposes only and are not intended to limit the present invention.

[0021] The following is an exemplary description of a method for preparing a highly dispersed organic-inorganic composite flexible thermoelectric material provided by the present invention, which may include the following steps.

[0022] (1) Carbon nanotubes coated with conjugated polymer A. Carbon nanotubes are added to a solution of conjugated polymer A for dispersion, centrifugation and collection of supernatant. Then the supernatant is cooled or evaporated and concentrated to precipitate solid. The solid is filtered and washed to remove most of the outer layer of conjugated polymer A until the part that cannot be washed away due to intermolecular forces is obtained, thus obtaining highly dispersed carbon nanotubes coated with a conjugated polymer A with a molecular layer thickness of A.

[0023] In some embodiments, the carbon nanotubes are single-walled carbon nanotubes with a diameter of 0.5–2 nm and a length of 20–30 nm.

[0024] In some embodiments, the conjugated polymer A can be an alkyl-substituted conjugated polymer with a molecular weight of 30,000-80,000, preferably polyalkylthiophene or polyalkylselenophene, more preferably one of butyl-substituted polythiophene, hexyl-substituted polythiophene, octyl-substituted polythiophene, octyl-substituted polyselenophene, dodecyl-substituted polythiophene, and dodecyl-substituted polyselenophene. When the conjugated polymer A undergoes supramolecular assembly with carbon nanotubes, the polymer's side chains need to have a certain length to encapsulate the carbon nanotubes and achieve effective dispersion. Therefore, the conjugated polymer A selected in this invention all have alkyl side chains. Simultaneously, to avoid affecting subsequent charge transport, the polymer's backbone structure needs to have a conjugated structure; therefore, polythiophene and polyselenophene are selected as the polymer backbone. Furthermore, if the molecular weight of the conjugated polymer A is too small, the degree of conjugation will decrease; if the molecular weight is too large, its solubility in solution will decrease.

[0025] In some embodiments, the mass ratio of the conjugated polymer A to carbon nanotubes can be 1:4 to 4:1, preferably 2:1. If the amount of conjugated polymer A is too small, the conjugated polymer will not be able to completely coat the carbon nanotubes, thus making it impossible to avoid the aggregation of carbon nanotubes; if the amount of conjugated polymer A is too large, it will cause the conjugated polymer itself to aggregate, which is not conducive to the interaction between the conjugated polymer and the carbon nanotubes, and is also not conducive to the dispersion of carbon nanotubes.

[0026] In some embodiments, the dispersion method can be pulsed ultrasonic dispersion, which can promote the formation of supramolecular self-assembly conditions between carbon nanotubes and conjugated polymer A; wherein the pulse power can be 100-1000w (e.g. 750w), the pulse temperature can be 20-80℃ (e.g. 50℃), and the pulse time can be 10-60min (e.g. 30min).

[0027] In the implementation of this scheme, if the power of pulsed ultrasonic dispersion is too low, the aggregated carbon nanotubes cannot be fully separated and cannot form sufficient contact with the polymer, resulting in incomplete coating of the carbon nanotubes and poor dispersibility. If the power of pulsed ultrasonic dispersion is too high, it will cause the polymer molecular chains to break. If the pulse temperature is too low, the thermal motion of the polymer molecular chains will be restricted, thus limiting the supramolecular interaction with the carbon nanotubes. If the pulse temperature is too high, the thermal motion of the polymer molecular chains will be intensified, making the molecular chains too flexible, making it difficult to form a stable core-shell structure with the carbon nanotubes, thus limiting the interaction. If the pulse time is too short, it will not be conducive to sufficient contact between the polymer and the carbon nanotubes; if the pulse time is too long, it will cause the system temperature to rise, limiting the interaction between the polymer and the carbon nanotubes.

[0028] In some embodiments, the centrifugation is performed using high-speed centrifugation; wherein the high-speed centrifugation speed can be 6000-15000 rpm (e.g., 12000 rpm), and the centrifugation time can be 10-60 min (e.g., 30 min).

[0029] In some embodiments, washing can be performed using a solvent at 20-70°C, ensuring that the filtrate is clear. The conjugated polymer A / carbon nanotubes are washed with a solvent at a specific temperature until all soluble components are removed, leaving only the coating layer with strong interaction with the carbon nanotubes. Preferably, the mass of the coating layer can be controlled to be less than 5% of the mass of the highly dispersed carbon nanotubes in the conjugated polymer A.

[0030] In some embodiments, the thickness of the molecular layer can range from 0.2 to 2 nm. After washing with a hot solvent, the conjugated polymer A coated onto the carbon nanotube mainly forms a stable structure with the carbon nanotube through intermolecular forces. The minimum thickness is the thickness of a single molecular layer, which, based on polymer bond lengths, is approximately 0.2 nm. Too many layers will weaken the intermolecular forces, making it impossible to form a stable coating structure.

[0031] The highly dispersed carbon nanotubes coated with conjugated polymer A provided by this invention exhibit uniform dispersion and no agglomeration, thus enabling the carbon nanotubes to be debonded through supramolecular self-assembly. Furthermore, the carbon nanotube material coated with conjugated polymer A prepared by the method provided by this invention demonstrates significantly better dispersion of carbon nanotubes compared to uncoated carbon nanotubes.

[0032] (2) Conductive polymer composite, film formation and doping. The highly dispersed carbon nanotubes of the coating molecular layer thickness conjugated polymer A are mixed with a solution of conductive polymer B to form a film-forming solution and a film is formed to obtain an organic-inorganic composite flexible thermoelectric film. Then, the organic-inorganic composite flexible thermoelectric film is immersed in a doping solution to obtain the highly dispersed organic-inorganic composite flexible thermoelectric material.

[0033] In some embodiments, the conductive polymer B may be at least one of polyaniline, polybenzofuranone, pyrrolopyrrole dione-based conductive polymer, and thiophene-based conductive polymer with a molecular weight of 30,000-100,000; preferably, the thiophene-based conductive polymer may be poly(3,4-dioxothiophene) or poly(3-hexylthiophene).

[0034] In some embodiments, the mass ratio of the highly dispersed carbon nanotubes of the coating molecular layer thickness conjugated polymer A to the conductive polymer B can be 1:4–4:1.

[0035] In some embodiments, the film formation method can be drop coating or spin coating. The film-forming solvent can be toluene, o-xylene, chloroform, or tetrahydrofuran. The film-forming temperature can be 20-60°C, and the film-forming time can be 0.1-12 hours. If the film-forming temperature is too low, the solvent will evaporate slowly, resulting in an excessively long film-forming time; if the film-forming temperature is too high, the solvent will evaporate too quickly, preventing the formation of a uniform film. Meanwhile, the film-forming method has a significant impact on the film-forming time. Generally, spin coating is faster, taking about 0.1 hours; while drop coating is determined by the corresponding film-forming temperature and solvent evaporation rate, typically between 0.5-12 hours.

[0036] In some embodiments, the doping solution can be an iron salt solution, preferably a ferric chloride or bis(trifluoromethanesulfonyl)imide iron solution, with a concentration of 0.1–1 mol / L (e.g., 0.5 mol / L), and the solvent can be nitromethane; the immersion time in the doping solution can be 0.1–4 h, preferably 0.5–4 h (e.g., 2 h); and the temperature of the doping solution can be 20–40 °C. Using an iron salt solution as the doping solution ensures a high degree of doping, resulting in high conductivity in the polymer after doping. However, too short a doping time leads to a low degree of doping and low polymer conductivity; too long a doping time can cause the polymer film to detach and break down.

[0037] The preparation method provided by this invention utilizes the intermolecular forces between carbon nanotubes and conjugated polymer A to form supramolecular self-assembly between carbon nanotubes and conjugated polymer A, achieving debinding of carbon nanotubes and significantly improving their dispersion while maintaining or enhancing their electrical transport properties. Simultaneously, the carbon nanotubes coated with conjugated polymer A provided by this invention can be composited with various typical conductive polymers B, resulting in a highly dispersed composite thermoelectric film with good carbon nanotube dispersion, a uniform and continuous film surface, and a significant improvement in thermoelectric performance. Furthermore, the process conditions used in this invention are simple, highly controllable, highly repeatable, and have low production costs, greatly expanding the practical application scope of carbon nanotube composite conjugated polymer thermoelectric materials.

[0038] The following examples further illustrate the present invention in detail. It should also be understood that the following examples are only for further explanation of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention fall within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not intended to be limited to the specific values ​​in the examples below.

[0039] Example 1

[0040] (1) Poly(3-dodecylthiophene) (P3DDT, regularity 98%, molecular weight 50,000) (20mg) was added to 50mL of toluene solvent to prepare a toluene solution of poly(3-dodecylthiophene). Then, 10mg of single-walled carbon nanotubes (SWNT) were added and dispersed by pulsed ultrasonication at a pulse power of 750w, a pulse temperature of 50℃, and a pulse time of 30min. The mixture was then centrifuged at 12000rpm for 30min to obtain the supernatant. The supernatant was incubated on ice overnight (10 hours) to precipitate the polymer-coated carbon nanotubes. The supernatant was filtered and washed with toluene at 50℃ until the filtrate was clear. The obtained filtrate was the carbon nanotubes coated with the molecular layer conjugated polymer. The molecular structure of P3DDT is as follows: (2) Carbon nanotubes coated with P3DDT molecular layer were mixed with poly(3-hexylthiophene) at mass ratios of 1:4, 1:2, 1:1, 2:1 and 4:1 to prepare thin films. The films were then placed in a 0.5 mol / L solution of bis(trifluoromethanesulfonyl)imide iron in nitromethane for 2 h to obtain a highly dispersed conductive poly(3-hexylthiophene) / P3DDT coated carbon nanotube composite flexible thermoelectric thin film material.

[0041] Following the aforementioned preparation process, uncoated polymer-coated carbon nanotubes were mixed with P3HT (poly-3-hexylthiophene) and P3DDT in the same proportion at the same mass fraction to form a film. The film was then placed in a 0.5 mol / L solution of bis(trifluoromethanesulfonyl)imide iron in nitromethane for 2 h to obtain a conductive poly-3-hexylthiophene / P3DDT / carbon nanotube composite film material as a comparison.

[0042] Tests showed that the thermoelectric properties of the polymer-coated composite film were significantly improved compared to the uncoated carbon nanotube composite film.

[0043] Example 2

[0044] (1) Poly(3-dodecylselenyl)phene (P3DDSe, regularity 98%, molecular weight 50,000) (20mg) was added to 50mL of toluene solvent to prepare a toluene solution of poly(3-dodecylselenyl)phene. 10mg of single-walled carbon nanotubes were added and dispersed by pulsed ultrasonication at a pulse power of 750w, a pulse temperature of 50℃, and a pulse time of 30min. The mixture was then centrifuged at 12000rpm for 30min to obtain the supernatant. The supernatant was incubated on ice overnight (10 hours) to precipitate the polymer-coated carbon nanotubes. The supernatant was filtered and washed with toluene at 50℃ until the filtrate was clear. The obtained filtrate was the carbon nanotubes coated by the molecular layer conjugated polymer. (2) Carbon nanotubes coated with the molecular layer P3DDSe were mixed with poly(3-hexylthiophene) at mass ratios of 1:4, 1:2, 1:1, 2:1 and 4:1 to prepare thin films. The films were then placed in a 0.5 mol / L solution of bis(trifluoromethanesulfonyl)imide iron in nitromethane for 2 h to obtain a highly dispersed conductive poly(3-hexylthiophene) / P3DDSe coated carbon nanotube composite flexible thermoelectric thin film material.

[0045] Following the aforementioned preparation process, uncoated carbon nanotubes were mixed with P3HT (poly-3-hexylthiophene) and P3DDSe in the same proportion at the same mass fraction to form a film. The film was then placed in a 0.5 mol / L solution of bis(trifluoromethanesulfonyl)imide iron in nitromethane for 2 h to obtain a conductive poly-3-hexylthiophene / P3DDSe / carbon nanotube composite film as a comparison.

[0046] Tests showed that the thermoelectric properties of the polymer-coated composite film were significantly improved compared to the uncoated carbon nanotube composite film.

[0047] Figure 1 This is a transmission electron microscope (TEM) image of the carbon nanotubes coated with conjugated polymer A prepared in Example 1 of this invention. As can be seen from the image, each carbon nanotube is coated with conjugated polymer A, and the diameter of the coated nanotubes is approximately 3-4 nm.

[0048] Figure 2These are atomic force microscopy images of carbon nanotubes before (a) and after (b) supramolecular assembly and dispersion in Example 1 of this invention. As can be seen from the images, before supramolecular assembly and dispersion, the carbon nanotubes, lacking the coating of conjugated polymer A, exhibit severe agglomeration, resulting in large nanotube bundle diameters of several hundred nanometers. In contrast, after supramolecular assembly, dispersion, and washing, the carbon nanotubes, with their outer layer coated by the conjugated polymer A, demonstrate good dispersibility, with nanotube bundle diameters in the tens of nanometers.

[0049] Figure 3 This diagram illustrates the thermoelectric properties of the polythiophene / carbon nanotube composite film (a) obtained without supramolecular assembly and dispersion, and the polythiophene / polymer-coated carbon nanotube composite film (b) obtained after supramolecular assembly and dispersion, in Example 1 of this invention. As can be seen from the figure, when carbon nanotubes and P3DDT-coated carbon nanotubes are combined with poly-3-hexylthiophene at the same mass ratio (50%), the thermoelectric properties of the composite film obtained with polymer-coated carbon nanotubes are significantly better than those of the film obtained without polymer-coated carbon nanotubes, almost twice as high. Meanwhile, as a control, the thermoelectric properties of polymer-coated P3DDT alone are very low, thus ruling out the introduction of P3DDT as the cause.

[0050] Although the present invention has been described in detail through the preferred embodiments above, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A method for preparing a highly dispersed organic-inorganic composite flexible thermoelectric material, characterized in that, include: (1) Carbon nanotubes are added to a solution of conjugated polymer A for dispersion, centrifugation and collection of supernatant. Then the supernatant is cooled or evaporated and concentrated to precipitate solid. The solid is filtered and washed to remove the outer layer of conjugated polymer A that is not bound to the carbon nanotubes by intermolecular forces, to obtain highly dispersed carbon nanotubes coated with conjugated polymer A with a molecular layer thickness of A. The conjugated polymer A is an alkyl-substituted conjugated polymer with a molecular weight of 30,000-80,000. The mass ratio of conjugated polymer A to carbon nanotubes is 1:4 to 4:

1. (2) The highly dispersed carbon nanotubes of the coating molecular layer thickness conjugated polymer A are mixed with the solution of conductive polymer B to form a film-forming solution and a film is formed to obtain an organic-inorganic composite flexible thermoelectric film. Then the organic-inorganic composite flexible thermoelectric film is immersed in a doping solution to obtain the highly dispersed organic-inorganic composite flexible thermoelectric material.

2. The preparation method according to claim 1, characterized in that, The carbon nanotubes are single-walled carbon nanotubes with a diameter of 0.5–2 nm and a length of 20–30 nm. The conjugated polymer A is polyalkylthiophene or polyalkylselene.

3. The preparation method according to claim 1, characterized in that, The conjugated polymer A is one of butyl-substituted polythiophene, hexyl-substituted polythiophene, octyl-substituted polythiophene, octyl-substituted polyselenophene, dodecyl-substituted polythiophene, and dodecyl-substituted polyselenophene.

4. The preparation method according to claim 1, characterized in that, The mass ratio of the conjugated polymer A to the carbon nanotubes is 2:

1.

5. The preparation method according to claim 1, characterized in that, The dispersion method is pulsed ultrasonic dispersion; wherein the pulse power is 100-1000 W, the pulse temperature is 20-80℃, and the pulse time is 10-60 min; The centrifugation is carried out using high-speed centrifugation; wherein the high-speed centrifugation speed is 6000-15000 rpm and the centrifugation time is 10-60 min.

6. The preparation method according to claim 1, characterized in that, Washing is performed using a solvent at 20-70℃; the mass ratio of the conjugated polymer A to the mass of the highly dispersed carbon nanotubes coated with the conjugated polymer A is controlled to be <5%; the thickness of the molecular layer is in the range of 0.2-2 nm.

7. The preparation method according to claim 1, characterized in that, The conductive polymer B is at least one of polyaniline, polybenzofuranone, pyrrolopyrrole dione-based conductive polymer, and thiophene-based conductive polymer with a molecular weight of 30,000-100,000; the thiophene-based conductive polymer is poly(3,4-dioxothiophene) or poly(3-hexylthiophene).

8. The preparation method according to claim 1, characterized in that, The mass ratio of the highly dispersed carbon nanotubes of the coating molecular layer thickness conjugated polymer A to the conductive polymer B is 1:4 to 4:

1.

9. The preparation method according to claim 1, characterized in that, The film formation method is drop coating or spin coating, the film formation solvent is toluene, o-xylene, chloroform or tetrahydrofuran, the film formation temperature is 20-60℃, and the film formation time is 0.1-12h.

10. The preparation method according to claim 1, characterized in that, The doping solution is an iron salt solution with a concentration of 0.1–1 mol / L and nitromethane as the solvent. The immersion time in the doping solution is 0.1–4 h, and the temperature of the doping solution is 20–40 °C.

11. The preparation method according to claim 10, characterized in that, The iron salt solution is ferric chloride and bis(trifluoromethanesulfonyl)imide iron solution.

12. A highly dispersed organic-inorganic composite flexible thermoelectric material obtained by the preparation method according to claim 1.

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