A gradient-doped semiconductor polymer thin film, a preparation method and application thereof

Abstract

The present application relates to a kind of gradient doped semiconductor polymer film and its preparation method and application, belong to organic thermoelectric material field.The gradient doped semiconductor polymer film includes semiconductor polymer film, and the dopant attached on all regions of the semiconductor polymer film;The doping degree of the dopant in each region of semiconductor polymer film overall presents ladder change, and the ladder change includes the gradient change of single dopant content formed on semiconductor polymer film or the gradient change of dopant kind.

Description

Technical Field

[0001] This invention belongs to the field of organic thermoelectric materials, specifically relating to a gradient-doped semiconductor polymer thin film, its preparation method, and its application. Background Technology

[0002] Thermoelectric materials are a class of semiconductor materials that enable the conversion between thermal and electrical energy based on the Seebeck and Peltier effects. They have significant application value in industrial waste heat power generation, electronic component cooling, and self-powered wearable devices. Compared with traditional inorganic thermoelectric materials, organic semiconductor thermoelectric materials, especially polymer semiconductor thermoelectric materials, have advantages such as easy processing (solution processing), low cost, readily available raw materials, and good flexibility, and are expected to be widely used in the field of novel flexible thermoelectric devices.

[0003] The thermoelectric conversion efficiency of polymer semiconductor materials is measured by the ZT value, ZT = S 2 σT / κ (where S, σ, and κ are the Seebeck coefficient, electrical conductivity, and thermal conductivity of the material, respectively). Due to the low intrinsic thermal conductivity of polymers and the difficulty in measuring it, the power factor PF (PF = S) is usually used. 2 The thermoelectric conversion capability of polymer materials is evaluated using σ. Therefore, an ideal thermoelectric material should possess a high Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Chemical doping can improve electrical conductivity by increasing the carrier concentration in the polymer film. However, the addition of a large amount of dopant causes dopant self-aggregation, disrupting the polymer's own arrangement and leading to a significant decrease in film mobility. Moreover, excessive doping exacerbates the reduction of the polymer band gap, making the Seebeck coefficient approach that of metallic materials (~10 μVK). -1 Ultimately, this does not effectively improve the thin film power factor. Therefore, achieving synergistic optimization of conductivity and Seebeck coefficient through reasonable doping methods is a research challenge and key focus in the field of organic thermoelectrics. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a gradient doping method and application that can simultaneously improve the conductivity and Seebeck coefficient of semiconductor polymer materials.

[0005] Specifically, in a first aspect, the present invention provides a gradient-doped semiconductor polymer film, comprising a semiconductor polymer film and a dopant attached to all regions of the semiconductor polymer film;

[0006] The doping degree of the dopant in different regions of the semiconductor polymer film generally exhibits a step-like variation, which includes a gradient change in the content of a single dopant or a gradient change in the types of dopant formed on the semiconductor polymer film.

[0007] Preferably, the semiconductor polymer is a conjugated polymer based on thiophene and its derivatives with alternating single and double bonds; more preferably, the side chains of the conjugated polymer have alkyl chains or alkoxy chains.

[0008] Preferably, the dopant is selected from ferric chloride, 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone, ferric trifluoromethylbenzenesulfonate, ferric methylbenzenesulfonate, nitrosine tetrafluoroborate, nitrosine hexafluorophosphate, C60, C70, C80, or substituted fullerene compounds.

[0009] Secondly, the present invention provides a method for preparing the above-mentioned gradient-doped semiconductor polymer thin film, comprising the following steps:

[0010] Semiconductor polymer solutions are coated onto a substrate by spin coating, drop coating, or dip coating. After the solvent evaporates, the substrate is thermally annealed in an anhydrous and oxygen-free atmosphere to prepare a semiconductor polymer film.

[0011] Prepare a dopant solution and perform single-dopant single-gradient doping, dual-dopant single-gradient doping, or multi-gradient doping on the semiconductor polymer film by vapor deposition or immersion method to obtain the gradient-doped semiconductor polymer film.

[0012] Preferably, the single-doper single-gradient doping step includes: preparing dopant solutions with lower concentration A1 and higher concentration A2 using a single doper; then, immersing the entire semiconductor polymer film in one of the doper solutions; and then immersing one end of the semiconductor polymer film, which has been completely immersed in one of the doper solutions, in the other doper solution, so that a gradient change in the content of the single doper is formed on the semiconductor polymer film, thereby obtaining a single-doper single-gradient doped semiconductor polymer film.

[0013] Preferably, in the single-doper single-gradient doping, the lower concentration of Al is 0.1 mg / mL. -1 ~5mg mL -1 The doping time for A1 concentration dopant solution is 10 s to 5 min; for higher concentration A2, it is 3 mg / mL. -1 ~20mg / mL -1 The doping time for A2 concentration dopant solution is 1 min to 30 min.

[0014] Preferably, the step of dual-doped single-gradient doping includes: preparing a dopant solution with the same concentration B using two different dopants; then, immersing the entire semiconductor polymer film in one of the dopant solutions; and then immersing one end of the semiconductor polymer film, which has been completely immersed in one of the dopant solutions, in the other dopant solution, so that a gradient change in the type of dopant is formed on the semiconductor polymer film, thereby obtaining a dual-doped single-gradient doped semiconductor polymer film.

[0015] Preferably, in the single-gradient doping of the dual dopant, the concentration B is 0.1 mg / mL. -1 ~20mg / mL -1 The time for a single doping is 10s-30min.

[0016] Preferably, the multi-gradient doping step includes: preparing three or more series of dopant solutions of different concentrations using a single dopant; then, completely immersing the semiconductor polymer film in one of the dopant solutions; next, sequentially immersing the semiconductor polymer film, which has been completely immersed in one of the dopant solutions, in other dopant solutions, thereby controlling the immersion depth of the film in dopant solutions of different concentrations to achieve gradient doping in different regions, resulting in a gradient change in the content of a single dopant on the semiconductor polymer film; or,

[0017] Three or more different dopants are used to prepare a series of dopant solutions of the same concentration. Then, the semiconductor polymer film is completely immersed in one of the dopant solutions. Next, the semiconductor polymer film that has been completely immersed in one of the dopant solutions is sequentially immersed in other dopant solutions. By controlling the immersion depth of the film in different types of dopant solutions, gradient doping in different regions is achieved, so that a gradient change of dopant type is formed on the semiconductor polymer film. A multi-gradient doped semiconductor polymer film is obtained.

[0018] Thirdly, the present invention provides an application of the above-mentioned gradient-doped semiconductor polymer thin film in organic thermoelectric conversion devices or organic field-effect transistor devices.

[0019] Beneficial effects

[0020] This invention introduces a doping gradient within the surface of a semiconductor polymer thin film. By utilizing the differences in carrier concentration, carrier mobility, carrier energy, and band structure on both sides of the gradient, the electrical conductivity and Seebeck coefficient of the material are simultaneously improved, significantly enhancing the thermoelectric performance of the polymer thin film material.

[0021] The preparation process of this invention is simple, and the gradient-doped semiconductor polymer film obtained by the preparation method disclosed in this invention has excellent thermoelectric properties and is expected to be widely used in high-performance polymer thermoelectric devices. Attached Figure Description

[0022] Figure 1 A schematic diagram of lightly doped and heavily doped sections in adjacent regions of a single-gradient doped semiconductor polymer film;

[0023] Figure 2 A schematic diagram illustrating the principle of measuring the Seebeck coefficient of gradient-doped semiconductor polymer thin film samples;

[0024] Figure 3 The weakly doped thin films (2 mg / mL) of Examples 10-11 and 13 -1 ), single-gradient doped thin films (2-5 mg / mL) -1 2-10 mg / mL -1 ) and dual-gradient doped films (2-5-10 mg mL) -1 Thermoelectric performance diagram. Detailed Implementation

[0025] The present invention will be further illustrated by the following embodiments. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the present invention.

[0026] The present invention provides a gradient-doped semiconductor polymer film, the gradient-doped semiconductor polymer film comprising a semiconductor polymer film and dopants attached to all regions of the semiconductor polymer film; the doping degree of the dopant in each region of the semiconductor polymer film generally exhibits a step-like variation, the step-like variation including a gradient variation in the content of a single dopant or a gradient variation in the types of dopants formed on the semiconductor polymer film.

[0027] This invention introduces a doping gradient within the surface of a semiconductor polymer film. By utilizing the differences in carrier concentration, carrier mobility, carrier energy, and band structure on both sides of the gradient, the electrical conductivity and Seebeck coefficient of the gradient-doped semiconductor polymer film material are simultaneously improved, significantly enhancing the thermoelectric performance of the semiconductor polymer film.

[0028] The semiconductor polymer is a conjugated polymer based on thiophene and its derivatives, characterized by alternating single and double bonds. Preferably, the side chains of the conjugated polymer contain alkyl or alkoxy chains, enabling it to dissolve in common organic solvents. This type of conjugated polymer has a low ionization energy and can achieve varying degrees of p-type doping under the action of dopants.

[0029] The length of the semiconductor polymer film can be 1mm-20mm, the width can be 1mm-20mm, and the thickness can be 10nm-100μm.

[0030] The dopant is a small molecule dopant. Preferably, the small molecule dopant may be selected from ferric chloride, 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone, ferric trifluoromethylbenzenesulfonate, ferric methylbenzenesulfonate, nitrosine tetrafluoroborate, nitrosine hexafluorophosphate, C60, C70, C80, or substituted fullerene compounds.

[0031] The following exemplarily illustrates a method for preparing gradient-doped semiconductor polymer films according to the present invention, which mainly includes the following steps.

[0032] (1) Semiconductor polymer film preparation. The semiconductor polymer is dissolved in a solvent formed by one or more of dichloromethane, chloroform, chlorobenzene, toluene or dichlorobenzene to obtain a semiconductor polymer solution; then, the semiconductor polymer solution is coated onto a substrate by spin coating, drop coating or dip coating, and after the solvent evaporates, it is thermally annealed in an anhydrous and oxygen-free atmosphere to prepare a dry semiconductor polymer film.

[0033] In some embodiments, the concentration of the semiconductor polymer solution can be 3 mg / mL. -1 ~15mg mL -1 The temperature of the heat annealing can be controlled between 100℃ and 250℃.

[0034] The substrate coated with the semiconductor polymer solution can be glass, silicon wafer, or a flexible substrate. In some embodiments, it can also be directly fabricated as a substrate-free, self-supporting semiconductor polymer film.

[0035] (2) Gradient doping of semiconductor polymer thin films. A dopant solution is prepared, and the semiconductor polymer thin film is subjected to single-dopant single-gradient doping, dual-dopant single-gradient doping, or multi-gradient doping by vapor deposition or immersion method to obtain the gradient-doped semiconductor polymer thin film.

[0036] The solvent used to prepare the dopant solution may be selected from at least one of acetone, chloroform, chlorobenzene, toluene, dichlorobenzene, acetonitrile, nitromethane, methanol, or ethanol.

[0037] The single-doped single-gradient doping can be achieved by the following steps: preparing dopant solutions with lower concentrations of A1 and higher concentrations of A2 using a single dopant; then immersing the entire semiconductor polymer film prepared in step (1) in one of the dopant solutions; next, immersing one end (a portion of the film) of the semiconductor polymer film that has been completely immersed in one of the dopant solutions in another dopant solution, so that a gradient change in the content of the single dopant is formed on the semiconductor polymer film, thereby obtaining a single-doped single-gradient doped semiconductor polymer film.

[0038] Doping with a lower concentration of A1 dopant solution can be called weak doping or light doping; doping with a higher concentration of A2 dopant solution can be called heavy doping.

[0039] In some embodiments, the low dopant solution concentration A1 used in the weak doping can be 0.1 mg / mL. -1 ~5mg mL -1 The weak doping time can be controlled to be 10s-5min; the higher dopant solution concentration A2 used in the heavy doping can be 3mg / mL. -1 ~20mg / mL -1 The time for heavy doping can be controlled from 1 min to 30 min.

[0040] The dual-doped single-gradient doping can be achieved by the following steps: preparing a dopant solution with the same concentration B using two different dopants; then immersing the entire semiconductor polymer film prepared in step (1) in one of the dopant solutions; next, immersing one end (a portion of the film) of the semiconductor polymer film that has been completely immersed in one of the dopant solutions in the other dopant solution, so that a gradient change in the type of dopant is formed on the semiconductor polymer film, thereby obtaining a dual-doped single-gradient doped semiconductor polymer film.

[0041] In some embodiments, the same concentration B can be controlled to be 0.1 mg / mL. -1 ~20mg / mL -1 The time for a single doping can be 10s-30min.

[0042] The concentration of the dopant solution and the doping time determine the degree of polymer doping. By controlling appropriate doping concentration and doping time, different doping degrees can be formed at both ends or in multiple regions of the same semiconductor polymer film, thereby enabling the gradient-doped semiconductor polymer film to exhibit higher thermoelectric properties and achieve better performance improvement.

[0043] The multi-gradient doping can be achieved by the following steps: preparing three or more series of dopant solutions of different concentrations using a single dopant; then immersing all the semiconductor polymer films prepared in step (1) in one of the dopant solutions; next, immersing the semiconductor polymer films that have been immersed in one of the dopant solutions in turn in other dopant solutions, and by controlling the immersion depth of the films in dopant solutions of different concentrations, gradient doping in different regions is achieved, so that a gradient change in the content of a single dopant is formed on the semiconductor polymer films; or, preparing a series of dopant solutions of the same concentration using three or more different dopants; then immersing all the semiconductor polymer films prepared in step (1) in one of the dopant solutions; next, immersing the semiconductor polymer films that have been immersed in one of the dopant solutions in turn in other dopant solutions, and by controlling the immersion depth of the films in different types of dopant solutions, gradient doping in different regions is achieved, so that a gradient change in the type of dopant is formed on the semiconductor polymer films; thus obtaining a multi-gradient doped semiconductor polymer film.

[0044] In the multi-gradient doping process, parameters such as the concentration and doping time of the relevant dopant solution can be referenced from those in the single-dopant single-gradient doping and dual-dopant single-gradient doping processes, and can be adaptively adjusted according to the requirements for improving the performance of the target material. The doping degree of the polymer film gradient change can be confirmed by ultraviolet-visible-near-infrared absorption spectroscopy. In some embodiments, the concentration of the lowest dopant solution among the three or more series of dopant solutions prepared using a single dopant can be controlled to be 0.1-5 mg / mL.

[0045] Figure 1 A schematic diagram of lightly doped and heavily doped sections in adjacent regions of a semiconductor polymer film with a single gradient doping is shown.

[0046] The gradient-doped semiconductor polymer thin film provided by this invention can be applied to organic thermoelectric conversion devices, organic field-effect transistor devices, etc. By simultaneously improving the Seebeck coefficient and conductivity of the semiconductor polymer thin film material, the performance of thermoelectric devices is optimized.

[0047] 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 are within the scope of protection of the present invention. The specific process parameters, etc., in the following examples are merely examples within the appropriate scope.

[0048] In this invention, the power factor PF = S is used. 2The power factor of the gradient-doped semiconductor polymer film is calculated using ×σ. Here, S represents the Seebeck coefficient, and σ represents the conductivity. The Seebeck coefficient of the polymer / polymer composite film is measured at specific points using a two-probe method, and the conductivity of the gradient-doped semiconductor polymer film is measured using a four-probe method. Figure 2 A schematic diagram of the Zebeck coefficient measurement principle for gradient-doped semiconductor polymer thin film samples is shown, where ΔT and ΔV are the temperature difference and voltage difference between the hot and cold ends measured between the two probes, respectively.

[0049] Example 1

[0050] Poly(3-hexylthiophene) (P3HT), with a number-average molecular weight of 25.12 kDa, was selected as the research subject, and its structure is as follows: P3HT.

[0051] The specific implementation steps are as follows: (1) Weigh an appropriate amount of P3HT and dissolve it in a solvent. Heat and stir until fully dissolved to obtain a concentration of 5 mg / mL. -1 A semiconductor polymer solution was drop-coated into a film. After the solvent evaporated completely, the film was annealed in an anhydrous and oxygen-free atmosphere to obtain a dry semiconductor polymer P3HT film with a thickness of 3 micrometers.

[0052] (2) Immerse the entire dried semiconductor polymer P3HT film in 2 mg mL of water. -1 The solution was placed in FeCl3 acetonitrile solution, and after 1 minute it was removed and dried to complete the weak doping process.

[0053] (3) Immerse one end of the weakly doped semiconductor polymer P3HT film in 5 mg mL -1 Gradient doping was performed in a FeCl3 acetonitrile solution, and the solution was removed and dried after 1 minute to complete the gradient doping process.

[0054] (4) Simultaneously, the entire semiconductor polymer P3HT film is immersed in 5 mg mL of water. -1 The FeCl3 acetonitrile solution was doped for 1 minute, then removed and dried for comparative experiments.

[0055] The conductivity of the P3HT polymer film after weak doping in step (2) was found to be 4.78 S cm⁻¹. -1 The Zebeck coefficient is 44.82 μV K. -1 The power factor is 0.93 μW / m. -1 K -2 The conductivity of the P3HT film after gradient doping in step (3) is 29.50 S cm⁻¹. -1 The Zebeck coefficient is 74.05 μV K. -1 The power factor is 16.55 μW / m. -1 K-2 The conductivity of the heavily doped P3HT polymer film in step (4) is 83.57 S cm⁻¹. -1 The Zebeck coefficient is 33.92 μV K. -1 The power factor is 9.62 μWm. -1 K -2 .

[0056] The test data above show that, compared to weakly doped polymer films, gradient-doped polymer films achieve simultaneous improvements in conductivity and Seebeck coefficient. Furthermore, the Seebeck coefficient and power factor of gradient-doped polymer films are the highest among weakly doped, heavily doped, and gradient-doped films.

[0057] Example 2

[0058] The research object and specific implementation steps of this embodiment are the same as those in Embodiment 1. The main difference is that the doping time in steps (3) and (4) is 3 minutes.

[0059] The conductivity of the P3HT polymer film after weak doping in step (2) was found to be 4.78 S cm⁻¹. -1 The Zebeck coefficient is 44.82 μV K. -1 The power factor is 0.93 μW / m. -1 K -2 The conductivity of the P3HT film after gradient doping in step (3) is 31.30 S cm⁻¹. -1 The Zebeck coefficient is 74.05 μV K. -1 The power factor is 16.96 μW / m. -1 K -2 The conductivity of the heavily doped P3HT polymer film in step (4) is 133.68 S cm⁻¹. -1 The Zebeck coefficient is 22.47 μV K. -1 The power factor is 6.68 μWm. -1 K -2 .

[0060] The test data above show that, compared to weakly doped polymer films, gradient-doped polymer films achieve simultaneous improvements in conductivity and Seebeck coefficient. Specifically, the Seebeck coefficient and power factor of the gradient-doped film are the highest among the weakly doped, heavily doped, and gradient-doped films.

[0061] Example 3

[0062] The research object and specific implementation steps of this embodiment are the same as those in Embodiment 1. The main difference is that the doping time in steps (3) and (4) is 5 minutes.

[0063] The conductivity of the P3HT polymer film after weak doping in step (2) was found to be 4.78 S cm⁻¹. -1 The Zebeck coefficient is 44.82 μV K. -1 The power factor is 0.93 μW / m. -1 K -2 The conductivity of the P3HT film after gradient doping in step (3) is 46.36 S cm⁻¹. -1 The Zebeck coefficient is 68.26 μV K. -1 The power factor is 21.28 μW / m. -1 K -2 The conductivity of the heavily doped P3HT polymer film in step (4) is 140.85 S cm⁻¹. -1 The Zebeck coefficient is 21.61 μV K. -1 The power factor is 6.54 μWm. -1 K -2 .

[0064] The test data above show that, compared to weakly doped polymer films, gradient-doped polymer films achieve simultaneous improvements in conductivity and Seebeck coefficient. Among these, the Seebeck coefficient and power factor of the gradient-doped films are the highest among the weakly doped, heavily doped, and gradient-doped films.

[0065] Example 4

[0066] The research object and specific implementation steps of this embodiment are the same as those in Embodiment 1. The main difference is that the doping time in steps (3) and (4) is 10 min.

[0067] The conductivity of the P3HT polymer film after weak doping in step (2) was found to be 4.78 S cm⁻¹. -1 The Zebeck coefficient is 44.82 μV K. -1 The power factor is 0.93 μW / m. -1 K -2 The conductivity of the P3HT film after gradient doping in step (3) is 79.62 S cm⁻¹. -1 The Zebeck coefficient is 59.05 μV K. -1 The power factor is 27.55 μW / m. -1 K -2 The conductivity of the heavily doped P3HT polymer film in step (4) is 173.20 S cm⁻¹. -1 The Zebeck coefficient is 17.85 μV K. -1 The power factor is 5.50 μWm. -1 K -2 .

[0068] The test data above show that, compared to weakly doped polymer films, gradient-doped polymer films achieve simultaneous improvements in conductivity and Seebeck coefficient. Furthermore, the Seebeck coefficient and power factor of the gradient-doped film are the highest among the weakly doped, heavily doped, and gradient-doped films.

[0069] Example 5

[0070] The polymer Pg32T-TT, containing alkoxy side chains, was selected as the research object, and its structure is as follows: Pg32T-TT. The material was prepared according to the method disclosed by Christian Müller et al. (Adv. Mater. 2017, 29, 1700930), and the polymer number-average molecular weight was 35.4 kDa.

[0071] The specific implementation steps are as follows: (1) Weigh an appropriate amount of Pg32T-TT and dissolve it in chlorobenzene. Heat and stir until fully dissolved to obtain a concentration of 5 mg / mL. -1 A semiconductor polymer solution was drop-coated into a film. After the solvent evaporated completely, the film was annealed in an anhydrous and oxygen-free atmosphere to obtain a dry semiconductor polymer Pg32T-TT film with a thickness of 5 micrometers.

[0072] (2) The dried semiconductor polymer Pg32T-TT film was completely immersed in 0.3 mg / mL water. -1 The weak doping process was completed by placing the sample in a 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone acetonitrile solution for 1 minute, then removing and drying it.

[0073] (3) Immerse one end of the weakly doped semiconductor polymer Pg32T-TT film in 20 mg mL -1 Gradient doping was performed on a solution of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone in acetonitrile, and the solution was removed and dried after 1 min to complete the gradient doping process.

[0074] (4) Simultaneously, the weakly doped semiconductor polymer Pg32T-TT film was immersed in 20 mg mL of water. -1 The mixture was doped in a solution of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone in acetonitrile for 1 minute, then removed and dried for use in a comparative experiment.

[0075] The conductivity of the weakly doped Pg32T-TT polymer film obtained by testing was 18.63 S cm⁻¹. -1 The Zebeck coefficient is 13.34 μV K. -1 The power factor is 0.34 μW / m. -1 K -2The conductivity of the Pg32T-TT film after gradient doping in step (3) is 108.23 S cm⁻¹. -1 The Zebeck coefficient is 52.06 μV K. -1 The power factor is 29.35 μW / m. -1 K -2 The conductivity of the heavily doped Pg32T-TT polymer film in step (4) is 178.63 S cm⁻¹. -1 The Zebeck coefficient is 3.79 μVK. -1 The power factor is 0.25 μW / m. -1 K -2 .

[0076] The test data above show that, compared to weakly doped polymer films, gradient-doped polymer films achieve simultaneous improvements in conductivity and Seebeck coefficient. Furthermore, the Seebeck coefficient and power factor of gradient-doped polymer films are the highest among weakly doped, heavily doped, and gradient-doped films.

[0077] Example 6

[0078] The research object and specific implementation steps of this embodiment are the same as those in Embodiment 5. The main difference is that the doping time in steps (3) and (4) is 3 minutes.

[0079] The conductivity of the weakly doped Pg32T-TT polymer film obtained by testing was 18.63 S cm⁻¹. -1 The Zebeck coefficient is 13.34 μV K. -1 The power factor is 0.34 μW / m. -1 K -2 The conductivity of the Pg32T-TT film after gradient doping in step (3) is 130.04 S cm⁻¹. -1 The Zebeck coefficient is 50.62 μV K. -1 The power factor is 34.73 μW / m. -1 K -2 The conductivity of the heavily doped Pg32T-TT polymer film in step (4) is 254.28 S cm⁻¹. -1 The Zebeck coefficient is 2.53 μVK. -1 The power factor is 0.16 μW / m. -1 K -2 .

[0080] The test data above show that, compared to weakly doped polymer films, gradient-doped polymer films achieve simultaneous improvements in conductivity and Seebeck coefficient. Specifically, the Seebeck coefficient and power factor of the gradient-doped film are the highest among the weakly doped, heavily doped, and gradient-doped films.

[0081] Example 7

[0082] The research object and specific implementation steps of this embodiment are the same as those in Embodiment 5. The main difference is that the doping time in steps (3) and (4) is 5 minutes.

[0083] The conductivity of the weakly doped Pg32T-TT polymer film obtained by testing was 18.63 S cm⁻¹. -1 The Zebeck coefficient is 13.34 μV K. -1 The power factor is 0.34 μW / m. -1 K -2 The conductivity of the Pg32T-TT thin film after gradient doping in step (3) is 248.96 S cm⁻¹. -1 The Zebeck coefficient is 40.14 μV K. -1 The power factor is 40.14 μW / m. -1 K -2 The conductivity of the heavily doped Pg32T-TT polymer film in step (4) is 297.71 S cm⁻¹. -1 The Zebeck coefficient is 2.26 μVK. -1 The power factor is 0.15 μW / m. -1 K -2 .

[0084] The test data above show that, compared to weakly doped polymer films, gradient-doped polymer films achieve simultaneous improvements in conductivity and Seebeck coefficient. Among these, the Seebeck coefficient and power factor of the gradient-doped films are the highest among the weakly doped, heavily doped, and gradient-doped films.

[0085] Example 8

[0086] The research object and specific implementation steps of this embodiment are the same as those in Embodiment 5. The main difference is that the doping time in steps (3) and (4) is 10 min.

[0087] The conductivity of the weakly doped Pg32T-TT polymer film obtained by testing was 18.63 S cm⁻¹. -1 The Zebeck coefficient is 13.34 μV K. -1 The power factor is 0.34 μW / m. -1 K -2 The conductivity of the Pg32T-TT thin film after gradient doping in step (3) is 195.46 S cm⁻¹. -1 The Zebeck coefficient is 40.77 μV K. -1 The power factor is 32.54 μW / m. -1 K -2The conductivity of the heavily doped Pg32T-TT polymer film in step (4) is 209.17 S cm⁻¹. -1 The Zebeck coefficient is 1.95 μVK. -1 The power factor is 0.08 μW / m. -1 K -2 .

[0088] The test data above show that, compared to weakly doped polymer films, gradient-doped polymer films achieve simultaneous improvements in conductivity and Seebeck coefficient. Furthermore, the Seebeck coefficient and power factor of the gradient-doped film are the highest among the weakly doped, heavily doped, and gradient-doped films.

[0089] Example 9

[0090] The classic donor-acceptor polymer PDPP-TT, containing alkyl-substituted pyrrolopyrrole dione units, was selected as the research subject, and its structure is as follows: PDPP-TT. The material was prepared according to the method disclosed by Iain McCulloch (J. Am. Chem. Soc. 2011, 133, 3272-3275), and the polymer number-average molecular weight was 71.1 kDa.

[0091] The specific implementation steps of this embodiment are the same as those in Embodiment 1. The main difference is that the concentration of the FeCl3 dopant solution in step (2) is 5 mg / mL. -1 In steps (3) and (4), the concentration of the FeCl3 dopant solution is 10 mg / mL. -1 .

[0092] The conductivity of the PDPP-TT polymer film after weak doping in step (2) was found to be 52.87 S cm⁻¹. -1 The Zebeck coefficient is 31.54 μV K. -1 The power factor is 5.26 μW / m. -1 K -2 The conductivity of the PDPP-TT film after gradient doping in step (3) is 55.55 S cm⁻¹. -1 The Zebeck coefficient is 91.94 μV K. -1 The power factor is 46.96 μW / m. -1 K -2 The conductivity of the heavily doped PDPP-TT polymer film in step (4) is 60.60 S cm⁻¹. -1 The Zebeck coefficient is 1.10 μVK. -1 The power factor is 0.007 μW / m. -1 K -2 .

[0093] The test data above show that, compared to weakly doped polymer films, gradient-doped polymer films achieve simultaneous improvements in conductivity and Seebeck coefficient. Furthermore, the Seebeck coefficient and power factor of gradient-doped polymer films are the highest among weakly doped, heavily doped, and gradient-doped films.

[0094] Example 10

[0095] Select the ternary random copolymer PDPP-g32T, which contains both donor-donor and donor-acceptor fragments. 0.35 As the subject of study, the structure is as follows: PDPP-g32T 0.35 The material was prepared according to the method disclosed by Li Hui et al. (Adv. Funct. Mater. 2020, 30, 2004378), and the polymer number-average molecular weight was 56.7 kDa.

[0096] The specific implementation steps in this embodiment are the same as in Embodiment 1.

[0097] Tests showed that the PDPP-g32T after weak doping in step (2) was... 0.35 The conductivity of the polymer film is 41.47 S cm⁻¹. -1 The Zebeck coefficient is 60.46 μV K. -1 The power factor is 15.34 μW / m. -1 K -2 Step (3) Gradient doping of PDPP-g32T 0.35 The conductivity of the thin film is 71.50 S cm⁻¹. -1 The Zebeck coefficient is 83.00 μV K. -1 The power factor is 49.82 μW / m. -1 K -2 Step (4) PDPP-g32T after heavy doping 0.35 The conductivity of the polymer film is 123.81 S cm⁻¹. -1 The Zebeck coefficient is 43.96 μVK. -1 The power factor is 23.93 μW / m. -1 K -2 .

[0098] The test data above show that, compared to weakly doped polymer films, gradient-doped polymer films achieve simultaneous improvements in conductivity and Seebeck coefficient. Furthermore, the Seebeck coefficient and power factor of gradient-doped polymer films are the highest among weakly doped, heavily doped, and gradient-doped films.

[0099] Example 11

[0100] The research object and specific implementation steps of this embodiment are the same as those in Embodiment 10. The main difference is that the concentration of the FeCl3 dopant solution in steps (3) and (4) is 10 mg / mL. -1 .

[0101] Tests showed that the PDPP-g32T after weak doping in step (2) was... 0.35 The conductivity of the polymer film is 41.47 S cm⁻¹. -1 The Zebeck coefficient is 60.46 μV K. -1 The power factor is 15.34 μW / m. -1 K -2 Step (3) Gradient doping of PDPP-g32T 0.35 The conductivity of the thin film is 115.23 S cm⁻¹. -1 The Zebeck coefficient is 65.85 μV K. -1 The power factor is 45.30 μW / m. - 1 K -2 Step (4) PDPP-g32T after heavy doping 0.35 The conductivity of the polymer film is 157.29 S cm⁻¹. -1 The Zebeck coefficient is 15.31 μVK. -1 The power factor is 3.69 μW / m. -1 K -2 .

[0102] The test data above show that, compared to weakly doped polymer films, gradient-doped polymer films achieve simultaneous improvements in conductivity and Seebeck coefficient. Furthermore, the Seebeck coefficient and power factor of the gradient-doped film are the highest among the weakly doped, heavily doped, and gradient-doped films.

[0103] Example 12

[0104] The research object and specific implementation steps of this embodiment are the same as those in Embodiment 10. The main difference is that the concentration of the FeCl3 dopant solution in steps (3) and (4) is 15 mg / mL. -1 .

[0105] Tests showed that the PDPP-g32T after weak doping in step (2) was... 0.35 The conductivity of the polymer film is 41.47 S cm⁻¹. -1 The Zebeck coefficient is 60.46 μV K. -1 The power factor is 15.34 μW / m. -1 K -2 Step (3) Gradient doping of PDPP-g32T 0.35 The conductivity of the thin film is 84.5 S cm⁻¹.-1 The Zebeck coefficient is 62.46 μV K. -1 The power factor is 30.01 μW / m. -1 K -2 Step (4) PDPP-g32T after heavy doping 0.35 The conductivity of the polymer film is 135.71 S cm⁻¹. -1 The Zebeck coefficient is 8.14 μVK. -1 The power factor is 0.90 μW / m. -1 K -2 .

[0106] The test data above show that, compared to weakly doped polymer films, gradient-doped polymer films achieve simultaneous improvements in conductivity and Seebeck coefficient. Furthermore, the Seebeck coefficient and power factor of the gradient-doped film are the highest among the weakly doped, heavily doped, and gradient-doped films.

[0107] Example 13

[0108] The research object in this embodiment is the same as that in embodiment 10.

[0109] The specific implementation steps are as follows: (1) Weigh an appropriate amount of PDPP-g32T 0.35 Dissolved in a solvent, heated and stirred until fully dissolved, yielding 5 mg / mL. -1 A semiconductor polymer solution was drop-coated into a film. After the solvent had completely evaporated, the film was thermally annealed in an anhydrous and oxygen-free atmosphere to obtain a dry semiconductor polymer PDPP-g32T with a thickness of 3 micrometers. 0.35 film;

[0110] (2) Dry PDPP-g32T 0.35 The entire film was immersed in 2 mg mL -1 The solution was placed in FeCl3 acetonitrile solution, and after 1 minute it was removed and dried to complete the weak doping process.

[0111] (3) The weakly doped semiconductor polymer PDPP-g32T 0.35 Two-thirds of the film was immersed in 5 mg mL -1 The FeCl3 acetonitrile solution was used for doping, and after 1 minute it was taken out and dried to complete the heavy doping process.

[0112] (4) The semiconductor polymer PDPP-g32T from step (3) 0.35 Half of the heavily doped section of the film (one-third of the total) was immersed in 10 mg mL -1 Dual gradient doping was performed in FeCl3 acetonitrile solution for 1 min.

[0113] (5) At the same time, PDPP-g32T0.35 The entire film is immersed in 10 mg mL -1 The FeCl3 acetonitrile solution was doped for 1 minute, then removed and dried for comparative experiments.

[0114] Tests showed that the PDPP-g32T after weak doping in step (2) was... 0.35 The conductivity of the polymer film is 41.47 S cm⁻¹. -1 The Zebeck coefficient is 60.46 μV K. -1 The power factor is 15.34 μW / m. -1 K -2 Step (3) PDPP-g32T after single-gradient doping 0.35 The conductivity of the thin film is 71.50 S cm⁻¹. -1 The Zebeck coefficient is 83.00 μV K. -1 The power factor is 49.82 μW / m. -1 K -2 Step (4) PDPP-g32T after dual gradient doping 0.35 The conductivity of the polymer film is 74.34 S cm⁻¹. -1 The Zebeck coefficient is 96.01 μV K. -1 The power factor is 68.51 μW / m. -1 K -2 Step (5) PDPP-g32T after heavy doping 0.35 The conductivity of the polymer film is 157.29 S cm⁻¹. -1 The Zebeck coefficient is 15.31 μV K. -1 The power factor is 3.69 μW / m. -1 K -2 Compared to weakly doped polymer films, both single-gradient doped and double-gradient doped films achieved simultaneous improvements in conductivity and Seebeck coefficient. Among these, double-gradient doping achieved a secondary improvement in both Seebeck coefficient and conductivity.

[0115] Figure 3 Weakly doped films (2 mg / mL) of Examples 10-11 and 13 are shown. -1 ), single-gradient doped thin films (2-5 mg / mL) -1 2-10 mg / mL -1 ) and dual-gradient doped films (2-5-10 mg mL) -1 The thermoelectric properties of the polymer semiconductor film are shown in the figure. As can be seen from the figure, compared to weakly doped films, gradient-doped films achieve simultaneous improvements in conductivity and Seebeck coefficient, and the thermoelectric properties of dual-gradient-doped films are superior to those of single-gradient-doped films.

[0116] Comparative Example 1

[0117] The comparative example studied the same object as in Example 5. The main difference is that the polymer film did not undergo a weak doping process; instead, one end of the film was directly immersed and doped.

[0118] The specific implementation steps are as follows: (1) Weigh an appropriate amount of Pg32T-TT and dissolve it in chlorobenzene. Heat and stir until fully dissolved to obtain a concentration of 5 mg / mL. -1 A semiconductor polymer solution was drop-coated into a film. After the solvent evaporated completely, the film was annealed in an anhydrous and oxygen-free atmosphere to obtain a dry semiconductor polymer Pg32T-TT film with a thickness of 5 micrometers.

[0119] (2) Immerse one end of the dried semiconductor polymer Pg32T-TT film in 5 mg mL of water. -1 The sample was placed in a FeCl3 acetonitrile solution, removed and dried after 1 minute to complete the gradient doping process.

[0120] (3) Simultaneously, the dried polymer Pg32T-TT film was completely immersed in 5 mg mL of water. -1 The sample was placed in a FeCl3 acetonitrile solution, dried after 1 minute, and used for a comparative experiment.

[0121] The conductivity of the Pg32T-TT polymer film directly gradient-doped in step (2) was found to be 24.88 S cm⁻¹. -1 The Zebeck coefficient is 50.01 μV K. -1 The power factor is 6.22 μW / m. -1 K -2 The conductivity of the heavily doped Pg32T-TT polymer film in step (3) is 178.63 S cm⁻¹. -1 The Zebeck coefficient is 3.79 μV K. -1 The power factor is 0.25 μW / m. -1 K -2 .

[0122] As can be seen from the above test data, although the Zebeck coefficient of the gradient-doped film in this comparative example is relatively high, its conductivity level is too low, resulting in a power factor that is much lower than that of the gradient-doped film described in Example 5.

[0123] Comparative Example 2

[0124] The research object and specific implementation steps of this comparative example are the same as those of Comparative Example 1. The main difference is that the doping time in steps (2) and (3) is 5 min.

[0125] The conductivity of the Pg32T-TT polymer film obtained by direct gradient doping in step (2) was 36.91 S cm⁻¹. -1The Zebeck coefficient is 46.11 μV K. -1 The power factor is 7.81 μW / m. -1 K -2 The conductivity of the heavily doped Pg32T-TT polymer film in step (3) is 297.71 S cm⁻¹. -1 The Zebeck coefficient is 2.26 μV K. -1 The power factor is 0.15 μW / m. -1 K -2 .

[0126] As can be seen from the above test data, although the Zebeck coefficient of the gradient-doped film in this comparative example is relatively high, its conductivity level is too low, resulting in a power factor that is much lower than that of the gradient-doped film described in Example 7.

[0127] Comparative Example 3

[0128] The research object and specific implementation steps of this comparative example are the same as those of Comparative Example 1. The main difference is that the doping time in steps (2) and (3) is 10 min.

[0129] The conductivity of the Pg32T-TT polymer film obtained by direct gradient doping in step (2) was found to be 30.65 S cm⁻¹. -1 The Zebeck coefficient is 40.24 μV K. -1 The power factor is 4.91 μW / m. -1 K -2 The conductivity of the heavily doped Pg32T-TT polymer film in step (3) is 209.17 S cm⁻¹. -1 The Zebeck coefficient is 1.95 μV K. -1 The power factor is 0.08 μW / m. -1 K -2 .

[0130] As can be seen from the above test data, the Zebeck coefficient of the gradient-doped film in this comparative example is close to that of Example 8, but the conductivity level is too low, resulting in its power factor being much lower than that of the gradient-doped film described in Example 8.

[0131] The above comparative examples show that an appropriate weak doping step or a step of first immersing the entire semiconductor thin film in a dopant solution can enable the thin film to obtain basic conductivity, and the formation of a doping gradient is a key factor in improving the thermoelectric performance of the thin film.

[0132] 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 gradient-doped semiconductor polymer thin film, characterized in that, The gradient-doped semiconductor polymer film includes a semiconductor polymer film and dopants attached to all regions of the semiconductor polymer film; the doping degree of the dopant in each region of the semiconductor polymer film generally exhibits a step-like variation, which includes a gradient variation in the content of a single dopant or a gradient variation in the types of dopants formed on the semiconductor polymer film. The preparation method includes the following steps: preparing a dopant solution, and performing single-dopant single-gradient doping, dual-dopant single-gradient doping, or multi-gradient doping on the semiconductor polymer film by vapor deposition or immersion method to obtain the gradient-doped semiconductor polymer film; The single-doper single-gradient doping step includes: preparing dopant solutions with lower concentrations A1 and higher concentrations A2 using a single dopant; then, completely immersing the semiconductor polymer film in one of the dopant solutions; next, immersing one end of the semiconductor polymer film, which has been completely immersed in one dopant solution, in the other dopant solution, thereby creating a gradient change in the content of the single dopant on the semiconductor polymer film, resulting in a single-doper single-gradient doped semiconductor polymer film; the lower concentration A1 is 0.1 mg / mL. -1 ~5mg mL -1 The doping time for A1 concentration dopant solution is 10 s to 5 min; for higher concentration A2, it is 3 mg / mL. -1 ~20mg / mL -1 The doping time for A2 concentration dopant solution is 1 min to 30 min; The steps of the dual-doped single-gradient doping method include: preparing dopant solutions of the same concentration B using two different dopants; then, completely immersing the semiconductor polymer film in one of the dopant solutions; next, immersing one end of the semiconductor polymer film, which has been completely immersed in one dopant solution, in the other dopant solution, thereby creating a gradient change in the dopant type on the semiconductor polymer film, resulting in a dual-doped single-gradient doped semiconductor polymer film; the concentration B is 0.1 mg / mL. -1 ~20 mg mL -1 The time for a single doping is 10s-30min; The multi-gradient doping steps include: preparing a series of dopant solutions of the same concentration using three or more different dopants; then immersing the entire semiconductor polymer film in one of the dopant solutions; next, immersing the semiconductor polymer film, which has been completely immersed in one of the dopant solutions, in other dopant solutions in sequence. By controlling the immersion depth of the film in different types of dopant solutions, gradient doping in different regions is achieved, so that a gradient change in the type of dopant is formed on the semiconductor polymer film, resulting in a multi-gradient doped semiconductor polymer film.

2. The preparation method according to claim 1, characterized in that, The semiconductor polymer film is made of a conjugated polymer based on thiophene and its derivatives, with alternating single and double bonds; the side chains of the conjugated polymer have alkyl or alkoxy chains.

3. The preparation method according to claim 1, characterized in that, The dopant is selected from ferric chloride, 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone, ferric trifluoromethylbenzenesulfonate, ferric methylbenzenesulfonate, nitrosine tetrafluoroborate, nitrosine hexafluorophosphate, C60, C70, C80 or substituted fullerene compounds.

4. The preparation method according to claim 1, characterized in that, The method for preparing the semiconductor polymer film includes the following steps: coating a semiconductor polymer solution onto a substrate by spin coating, drop coating or dip coating, and after the solvent evaporates, performing thermal annealing in an anhydrous and oxygen-free atmosphere to obtain a semiconductor polymer film.

5. The preparation method according to claim 1, characterized in that, The multi-gradient doping steps include: preparing three or more series of dopant solutions of different concentrations using a single dopant; then immersing the entire semiconductor polymer film in one of the dopant solutions; next, immersing the semiconductor polymer film, which has been completely immersed in one of the dopant solutions, sequentially immersing it in other dopant solutions. By controlling the immersion depth of the film in dopant solutions of different concentrations, gradient doping in different regions is achieved, resulting in a gradient change in the content of a single dopant on the semiconductor polymer film, thus obtaining a multi-gradient doped semiconductor polymer film.

6. The application of a gradient-doped semiconductor polymer thin film obtained by the preparation method of claim 1 in organic thermoelectric conversion devices or organic field-effect transistor devices.

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