A flexible PEDOT:PSS thermoelectric thin film with high thermoelectric performance and high air stability, its preparation method and application

Abstract

This invention discloses a flexible PEDOT:PSS thermoelectric thin film with high thermoelectric performance and high air stability, its preparation method, and its applications. One preparation method involves forming a PEDOT:PSS thin film on a substrate, treating the film with a reducing solution, and then further treating it with concentrated sulfuric acid. Another preparation method involves forming a PEDOT:PSS thin film on a substrate, treating the film with a polar solvent, further treating it with a reducing solution, and then treating it with concentrated sulfuric acid. The polar solvent has high polarity and high dielectric constant. When treating the film, it introduces a shielding effect into the PEDOT:PSS, removing the insulating PSS and thus improving the conductivity. Treating the PEDOT:PSS thin film with a reducing solution can reduce the oxidation level of PEDOT in the film and improve the Seebeck coefficient. Treatment with concentrated sulfuric acid, due to the oxidation effect of concentrated sulfuric acid, increases the proportion of bipolar PEDOT in the film, significantly improving the conductivity of the film. The PEDOT in the film is in an oxidation / reduction equilibrium state, and when the film is exposed to air, its thermoelectric performance remains essentially unchanged.

Description

Technical Field

[0001] This invention belongs to the field of flexible thermoelectric material preparation technology, specifically relating to a PEDOT:PSS flexible thermoelectric thin film with high thermoelectric performance and high air stability, its preparation method and application. Background Technology

[0002] With the rapid development of the Internet of Things (IoT), the demand for self-powered technologies, such as flexible wearable and implantable electronic devices, has increased dramatically. Flexible thermoelectric materials can directly convert low-grade waste heat, such as human body temperature or environmental waste heat, into electrical energy, thereby providing continuous power support for various flexible electronic devices. Compared with traditional high-performance inorganic thermoelectric materials, conductive polymers generally have lower thermoelectric properties, but due to their excellent flexibility and ultra-low thermal conductivity, they are still widely considered to be highly promising flexible thermoelectric materials.

[0003] Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) has become the most studied flexible conductive polymer thermoelectric material system due to its commercialization, ease of processing, ultra-low thermal conductivity, and excellent flexibility. However, the original PEDOT:PSS has limited electrical conductivity (<1 S cm⁻¹). -1 ) and Seebeck coefficient (15~18μV K) -1 The oxidation or reduction of PEDOT:PSS is generally poor, resulting in low overall thermoelectric performance. Therefore, further improvement of these key parameters is needed to achieve higher thermoelectric performance. Literature (Adv. Energy Mater. 2017, 1602116; Energy Environ. Sci., 2020, 13, 3480-3488) typically employs a combined doping and dedoping strategy to adjust the oxidation or reduction degree of PEDOT:PSS, thereby controlling its carrier transport behavior and achieving decoupling of conductivity and Seebeck coefficient to improve its overall thermoelectric performance. For example, literature (Chem. Mater. 2019, 31, 14, 5238-5244) first uses formamide and concentrated sulfuric acid to dope PEDOT:PSS in two steps to increase conductivity to a sufficiently high level, and then uses sodium borohydride to dedope and improve the Seebeck coefficient, achieving high thermoelectric performance at room temperature.

[0004] However, PEDOT:PSS also exhibits low air stability; its thermoelectric properties rapidly degrade with prolonged exposure to air. A report (Journal of Materials Chemistry C. 2014; 2:1278-83.) indicates that dedoped PEDOT:PSS exposed to air increases the oxidation of PEDOT, causing a sharp drop in the Seebeck coefficient within just one day. The report emphasizes that even encapsulation techniques or inert atmospheres cannot completely prevent this air degradation. Furthermore, existing literature (Advanced Electronic Materials. 2020; 6:2000620) uses in-situ photoelectron spectroscopy to discover that the hydrophilic PSS in PEDOT:PSS absorbs water, altering the molecular structure and leading to conductivity degradation. This confirms that the air degradation of PEDOT:PSS is related to its PSS content. When PEDOT:PSS is redoped with methanol, its molecular structure is readjusted, and some thermoelectric properties are restored, but they remain lower than before air degradation. Therefore, preparing PEDOT:PSS with both high thermoelectric properties and high air stability is an important problem that urgently needs to be solved for this material to be applied in practice. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a PEDOT:PSS flexible thermoelectric film with high thermoelectric performance and high air stability, its preparation method and application, so as to solve the problem that the prior art cannot simultaneously make PEDOT:PSS film have both high thermoelectric performance and high air stability.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a method for preparing a flexible PEDOT:PSS thermoelectric thin film with high thermoelectric performance and high air stability, comprising the following two methods:

[0008] Method I:

[0009] 1) PEDOT:PSS aqueous solution is uniformly dropped onto the substrate and dried to form a PEDOT:PSS film, resulting in film A;

[0010] 2) Thin film A is soaked, drip-cast, or spin-coated with a reducing solution, and then rinsed to obtain thin film B;

[0011] 3) Concentrated sulfuric acid was dropped onto the surface of film B under heating, rinsed, dried, and the substrate was removed to obtain PEDOT:PSS flexible thermoelectric film C.

[0012] Method II:

[0013] 1) PEDOT:PSS aqueous solution is uniformly dropped onto the substrate and dried to form a PEDOT:PSS film, resulting in film A;

[0014] 2) Thin film A is immersed, drop-cast, or spin-coated with a polar solvent, and then rinsed to obtain thin film D;

[0015] 3) The film D is soaked, drip-cast, or spin-coated with a reducing solution, and then rinsed to obtain film E;

[0016] 4) Concentrated sulfuric acid was dropped onto the surface of film E under heating, rinsed, dried, and the substrate was removed to obtain PEDOT:PSS flexible thermoelectric film F.

[0017] Preferably, in step 1) of methods I and II, the substrate is first cleaned with deionized water, acetone and isopropanol in sequence, then dried, and then the PEDOT:PSS aqueous solution is evenly dropped onto the obtained substrate.

[0018] Preferably, in methods I and II, the reducing solution is composed of a solution containing a reducing agent, including a solution composed of a reducing agent and deionized water, a solution composed of a polar solvent and a reducing agent, or a solution composed of a polar solvent, deionized water, and a reducing agent.

[0019] Preferably, the reducing agent is sodium hydroxide, sodium borohydride, sodium bicarbonate, sodium sulfite, hydrazine, or L-ascorbic acid.

[0020] Preferably, in step 2) of method II, the polar solvent is dimethyl sulfoxide, dimethylformamide, dimethylacetamide, ethylene glycol, or formamide.

[0021] Preferably, in methods I and II, the soaking time with a reducing solution is 10–60 min.

[0022] Preferably, in methods I and II, 100–300 μL of concentrated sulfuric acid is added dropwise, the heating temperature is 120–180 °C, and the time is 10–80 min.

[0023] Preferably, in methods I and II, after rinsing with concentrated sulfuric acid, the mixture is dried at 60–80°C for 10–20 min.

[0024] The present invention also discloses the PEDOT:PSS flexible thermoelectric thin film prepared by the above preparation method.

[0025] This invention also discloses the application of the above-mentioned PEDOT:PSS flexible thermoelectric film in the fabrication of thermoelectric devices, optoelectronic devices, and perovskite solar cells.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] This invention discloses a method for preparing a flexible PEDOT:PSS thermoelectric thin film with high thermoelectric performance and high air stability. One method involves uniformly dropping a PEDOT:PSS aqueous solution onto a substrate and drying it to form a PEDOT:PSS thin film. The film is then treated with a reducing solution and further treated with concentrated sulfuric acid. Another method involves first forming a PEDOT:PSS thin film on a substrate, treating it with a polar solvent, further treating it with a reducing solution, and then treating it with concentrated sulfuric acid. Because the polar solvent has high polarity and a high dielectric constant, it introduces a shielding effect into the PEDOT:PSS during treatment, removing the insulating PSS and thus improving conductivity. Treating the PEDOT:PSS thin film with a reducing solution reduces the oxidation level of PEDOT in the film, increasing the Seebeck coefficient. Further treatment with concentrated sulfuric acid, due to its oxidizing effect, increases the proportion of bipolar PEDOT in the film, significantly improving conductivity and air stability. Ultimately, PEDOT is in a state of oxidation / reduction equilibrium. When the film is exposed to air, it is not affected by oxygen and moisture in the air, and its thermoelectric properties remain essentially unchanged. PEDOT:PSS film has both high thermoelectric properties and high air stability.

[0028] Furthermore, the H2SO4 treatment time is 10–80 min. With the increase of treatment time, the oxidation effect of H2SO4 is more complete.

[0029] Furthermore, by adding concentrated sulfuric acid dropwise under heating conditions, H2SO4 can fully react with PEDOT to increase the proportion of bipolarons in PEDOT and improve the conductivity of the film.

[0030] This invention also discloses a flexible thermoelectric film of PEDOT:PSS with high thermoelectric performance and high air stability. In the continuous two-step process of reduction and oxidation of the PEDOT:PSS film, after the second step of H2SO4 oxidation treatment for 60 min, the film has a conductivity of ~2627 S / cm, a Seebeck coefficient of ~17 μV / K, and a maximum power factor of ~76 μW / m / K. 2 This power factor is nearly 38% higher than that of the film treated in the first step only in a reducing solution, demonstrating that the two-step reduction / oxidation treatment of PEDOT:PSS films can significantly improve thermoelectric performance. Furthermore, the power factor of the PEDOT:PSS film treated with H2SO4 for 30 min and then exposed to air for 15 days remained at ~48 μW / m / K. 2Nearby, the oxidation / reduction levels of the PEDOT:PSS film remain largely unchanged, thus achieving a balance between high thermoelectric performance and excellent air stability. Attached Figure Description

[0031] Figure 1 The graph shows the relationship between the conductivity, Seebeck coefficient, and power factor of the PEDOT:PSS flexible thermoelectric films obtained in Examples 1-9 of this invention and the treatment time with concentrated sulfuric acid.

[0032] Figure 2 The graph shows the trend of change in conductivity, Seebeck coefficient, and power factor of the PEDOT:PSS flexible thermoelectric film obtained in Example 1 of the present invention after being exposed to air for 15 days.

[0033] Figure 3 The graph shows the trend of change in conductivity, Seebeck coefficient, and power factor of the PEDOT:PSS flexible thermoelectric film obtained in Example 4 of the present invention after being exposed to air for 15 days.

[0034] Figure 4 The graph shows the trend of change in conductivity, Seebeck coefficient, and power factor of the PEDOT:PSS flexible thermoelectric film obtained in Example 7 of the present invention after being exposed to air for 7 days.

[0035] Figure 5 The images show a comparison of the Raman spectra of the PEDOT:PSS flexible thermoelectric films obtained in Examples 1, 4, and 7 of this invention and the original films. Detailed Implementation

[0036] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0037] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0038] This invention discloses a method for preparing a flexible PEDOT:PSS thermoelectric thin film with high thermoelectric performance and high air stability, comprising the following steps:

[0039] Step 1: Clean the glass substrate in sequence with deionized water, acetone, and isopropanol, and then dry it;

[0040] Step 2: Drop-coat 300 μL of PEDOT:PSS aqueous solution (Clevious PH1000) onto the glass substrate obtained in Step 1, place it in a vacuum drying oven, and dry at 60°C for 12 h to obtain film A;

[0041] Step 3: Immerse the film A obtained in Step 2 in a DMAC / H2O / LAA solution for 10 min, wherein the volume ratio of DMAC to H2O is 4:1 and the concentration of LAA is 0.5 mol / L. -1 Afterwards, it was removed, rinsed three times with deionized water, and dried at 80°C for 20 minutes to form a PEDOT:PSS thermoelectric film B on the glass substrate. (The DMAC / H2O / LAA solution is a mixed solution composed of dimethylacetamide, deionized water, and L-ascorbic acid.)

[0042] Step 4: Add 100-300 μL of concentrated sulfuric acid to the film obtained in Step 3 on a heating stage at 120-180℃, keep it for 10-80 min, rinse it 4 times with deionized water, dry it at 60-80℃ for 10-20 min, and then remove the glass substrate to obtain PEDOT:PSS flexible thermoelectric film C.

[0043] Example 1

[0044] Step 1: Clean the glass substrate in sequence with deionized water, acetone, and isopropanol, and then dry it;

[0045] Step 2: Drop-coat 300 μL of PEDOT:PSS aqueous solution (Clevious PH1000) onto the glass substrate obtained in Step 1, place it in a vacuum drying oven, and dry at 60°C for 12 h to obtain film A;

[0046] Step 3: Immerse the film A obtained in Step 2 in a DMAC / H2O / LAA solution for 10 min, wherein the ratio of DMAC to H2O is 4:1 and the concentration of LAA is 0.5 mol / L. -1 Afterwards, it is removed, rinsed three times with deionized water, and dried at 80°C for 20 minutes to form a PEDOT:PSS thermoelectric film B on the glass substrate. (The DMAC / H2O / LAA solution is a mixed solution composed of dimethylacetamide, deionized water, and L-ascorbic acid).

[0047] Example 2

[0048] Step 1: Clean the glass substrate in sequence with deionized water, acetone, and isopropanol, and then dry it;

[0049] Step 2: Drop-coat 300 μL of PEDOT:PSS aqueous solution (Clevious PH1000) onto the glass substrate obtained in Step 1, place it in a vacuum drying oven, and dry at 60°C for 12 h to obtain film A;

[0050] Step 3: Immerse the film A obtained in Step 2 in a DMAC / H2O / LAA solution for 10 min, wherein the ratio of DMAC to H2O is 4:1 and the concentration of LAA is 0.5 mol / L. -1 Afterwards, it was removed, rinsed three times with deionized water, and dried at 80°C for 20 minutes to form a PEDOT:PSS thermoelectric film B on the glass substrate. (The DMAC / H2O / LAA solution is a mixed solution composed of dimethylacetamide, deionized water, and L-ascorbic acid.)

[0051] Step 4: Add 300 μL of concentrated sulfuric acid to the film obtained in Step 3 on a heating stage at 160°C, keep it for 10 min, rinse it 4 times with deionized water, dry it at 80°C for 20 min, and then remove the glass substrate to obtain PEDOT:PSS flexible thermoelectric film C.

[0052] Example 3

[0053] Step 1: Clean the glass substrate in sequence with deionized water, acetone, and isopropanol, and then dry it;

[0054] Step 2: Drop-coat 300 μL of PEDOT:PSS aqueous solution (Clevious PH1000) onto the glass substrate obtained in Step 1, place it in a vacuum drying oven, and dry at 60°C for 12 h to obtain film A;

[0055] Step 3: Immerse the film A obtained in Step 2 in a DMAC / H2O / LAA solution for 10 min, wherein the ratio of DMAC to H2O is 4:1 and the concentration of LAA is 0.5 mol / L. -1 Afterwards, it was removed, rinsed three times with deionized water, and dried at 80°C for 20 minutes to form a PEDOT:PSS thermoelectric film B on the glass substrate. (The DMAC / H2O / LAA solution is a mixed solution composed of dimethylacetamide, deionized water, and L-ascorbic acid.)

[0056] Step 4: Add 300 μL of concentrated sulfuric acid to the film obtained in Step 3 on a heating stage at 160°C, keep it for 20 min, rinse it 4 times with deionized water, dry it at 80°C for 20 min, and then remove the glass substrate to obtain PEDOT:PSS flexible thermoelectric film C.

[0057] Example 4

[0058] Step 1: Clean the glass substrate in sequence with deionized water, acetone, and isopropanol, and then dry it;

[0059] Step 2: Drop-coat 300 μL of PEDOT:PSS aqueous solution (Clevious PH1000) onto the glass substrate obtained in Step 1, place it in a vacuum drying oven, and dry at 60°C for 12 h to obtain film A;

[0060] Step 3: Immerse the film A obtained in Step 2 in a DMAC / H2O / LAA solution for 10 min, wherein the ratio of DMAC to H2O is 4:1 and the concentration of LAA is 0.5 mol / L. -1 Afterwards, it was removed, rinsed three times with deionized water, and dried at 80°C for 20 minutes to form a PEDOT:PSS thermoelectric film B on the glass substrate. (The DMAC / H2O / LAA solution is a mixed solution composed of dimethylacetamide, deionized water, and L-ascorbic acid.)

[0061] Step 4: Add 300 μL of concentrated sulfuric acid to the film obtained in Step 3 on a heating stage at 160°C, keep it for 30 min, rinse it 4 times with deionized water, dry it at 80°C for 20 min, and then remove the glass substrate to obtain PEDOT:PSS flexible thermoelectric film C.

[0062] Example 5

[0063] Step 1: Clean the glass substrate in sequence with deionized water, acetone, and isopropanol, and then dry it;

[0064] Step 2: Drop-coat 300 μL of PEDOT:PSS aqueous solution (Clevious PH1000) onto the glass substrate obtained in Step 1, place it in a vacuum drying oven, and dry at 60°C for 12 h to obtain film A;

[0065] Step 3: Immerse the film A obtained in Step 2 in a DMAC / H2O / LAA solution for 10 min, wherein the ratio of DMAC to H2O is 4:1 and the concentration of LAA is 0.5 mol / L. -1 Afterwards, it was removed, rinsed three times with deionized water, and dried at 80°C for 20 minutes to form a PEDOT:PSS thermoelectric film B on the glass substrate. (The DMAC / H2O / LAA solution is a mixed solution composed of dimethylacetamide, deionized water, and L-ascorbic acid.)

[0066] Step 4: Add 300 μL of concentrated sulfuric acid to the film obtained in Step 3 on a heating stage at 160°C, keep it for 40 min, rinse it 4 times with deionized water, dry it at 80°C for 20 min, and then remove the glass substrate to obtain PEDOT:PSS flexible thermoelectric film C.

[0067] Example 6

[0068] Step 1: Clean the glass substrate in sequence with deionized water, acetone, and isopropanol, and then dry it;

[0069] Step 2: Drop-coat 300 μL of PEDOT:PSS aqueous solution (Clevious PH1000) onto the glass substrate obtained in Step 1, place it in a vacuum drying oven, and dry at 60°C for 12 h to obtain film A;

[0070] Step 3: Immerse the film A obtained in Step 2 in a DMAC / H2O / LAA solution for 10 min, wherein the ratio of DMAC to H2O is 4:1 and the concentration of LAA is 0.5 mol / L. -1 Afterwards, it was removed, rinsed three times with deionized water, and dried at 80°C for 20 minutes to form a PEDOT:PSS thermoelectric film B on the glass substrate. (The DMAC / H2O / LAA solution is a mixed solution composed of dimethylacetamide, deionized water, and L-ascorbic acid.)

[0071] Step 4: Add 300 μL of concentrated sulfuric acid to the film obtained in Step 3 on a heating stage at 160°C, keep it for 50 min, rinse it 4 times with deionized water, dry it at 80°C for 20 min, and then remove the glass substrate to obtain PEDOT:PSS flexible thermoelectric film C.

[0072] Example 7

[0073] Step 1: Clean the glass substrate in sequence with deionized water, acetone, and isopropanol, and then dry it;

[0074] Step 2: Drop-coat 300 μL of PEDOT:PSS aqueous solution (Clevious PH1000) onto the glass substrate obtained in Step 1, place it in a vacuum drying oven, and dry at 60°C for 12 h to obtain film A;

[0075] Step 3: Immerse the film A obtained in Step 2 in a DMAC / H2O / LAA solution for 10 min, wherein the ratio of DMAC to H2O is 4:1 and the concentration of LAA is 0.5 mol / L. -1 Afterwards, it was removed, rinsed three times with deionized water, and dried at 80°C for 20 minutes to form a PEDOT:PSS thermoelectric film B on the glass substrate. (The DMAC / H2O / LAA solution is a mixed solution composed of dimethylacetamide, deionized water, and L-ascorbic acid.)

[0076] Step 4: Add 300 μL of concentrated sulfuric acid to the film obtained in Step 3 on a heating stage at 160°C, keep it for 60 min, rinse it 4 times with deionized water, dry it at 80°C for 20 min, and then remove the glass substrate to obtain PEDOT:PSS flexible thermoelectric film C.

[0077] Example 8

[0078] Step 1: Clean the glass substrate in sequence with deionized water, acetone, and isopropanol, and then dry it;

[0079] Step 2: Drop-coat 300 μL of PEDOT:PSS aqueous solution (Clevious PH1000) onto the glass substrate obtained in Step 1, place it in a vacuum drying oven, and dry at 60°C for 12 h to obtain film A;

[0080] Step 3: Immerse the film A obtained in Step 2 in a DMAC / H2O / LAA solution for 10 min, wherein the ratio of DMAC to H2O is 4:1 and the concentration of LAA is 0.5 mol / L. -1 Afterwards, it was removed, rinsed three times with deionized water, and dried at 80°C for 20 minutes to form a PEDOT:PSS thermoelectric film B on the glass substrate. (The DMAC / H2O / LAA solution is a mixed solution composed of dimethylacetamide, deionized water, and L-ascorbic acid.)

[0081] Step 4: Add 300 μL of concentrated sulfuric acid to the film obtained in Step 3 on a heating stage at 160°C, keep it for 70 min, rinse it 4 times with deionized water, dry it at 80°C for 20 min, and then remove the glass substrate to obtain PEDOT:PSS flexible thermoelectric film C.

[0082] Example 9

[0083] Step 1: Clean the glass substrate in sequence with deionized water, acetone, and isopropanol, and then dry it;

[0084] Step 2: Drop-coat 300 μL of PEDOT:PSS aqueous solution (Clevious PH1000) onto the glass substrate obtained in Step 1, place it in a vacuum drying oven, and dry at 60°C for 12 h to obtain film A;

[0085] Step 3: Immerse the film A obtained in Step 2 in a DMAC / H2O / LAA solution for 10 min, wherein the ratio of DMAC to H2O is 4:1 and the concentration of LAA is 0.5 mol / L. -1 Afterwards, it was removed, rinsed three times with deionized water, and dried at 80°C for 20 minutes to form a PEDOT:PSS thermoelectric film B on the glass substrate. (The DMAC / H2O / LAA solution is a mixed solution composed of dimethylacetamide, deionized water, and L-ascorbic acid.)

[0086] Step 4: Add 300 μL of concentrated sulfuric acid to the film obtained in Step 3 on a heating stage at 160°C, keep it for 80 min, rinse it 4 times with deionized water, dry it at 80°C for 20 min, and then remove the glass substrate to obtain PEDOT:PSS flexible thermoelectric film C.

[0087] Example 10

[0088] Step 1: Clean the glass substrate in sequence with deionized water, acetone, and isopropanol, and then dry it;

[0089] Step 2: Drop-coat 300 μL of PEDOT:PSS aqueous solution (Clevious PH1000) onto the glass substrate obtained in Step 1, place it in a vacuum drying oven, and dry at 60°C for 12 h to obtain film A;

[0090] Step 3: Immerse the film A obtained in Step 2 in formamide for 20 minutes, then take it out, rinse it three times with deionized water, and dry it at 80°C for 10 minutes to form a PEDOT:PSS thermoelectric film D on the glass substrate.

[0091] Step 4: Immerse the thin film D obtained in Step 3 in 0.1 mol L... -1 After soaking in NaOH solution for 30 minutes, the film was rinsed four times with deionized water and dried at 80°C for 10 minutes to obtain film E.

[0092] Step 5: Add 100 μL of concentrated sulfuric acid to the film E obtained in Step 4 on a heating stage at 120°C, keep it for 60 min, rinse it 4 times with deionized water, dry it at 60°C for 10 min, and then remove the glass substrate to obtain the PEDOT:PSS flexible thermoelectric film F.

[0093] Example 11

[0094] Step 1: Clean the glass substrate in sequence with deionized water, acetone, and isopropanol, and then dry it;

[0095] Step 2: Drop-coat 300 μL of PEDOT:PSS aqueous solution (Clevious PH1000) onto the glass substrate obtained in Step 1, place it in a vacuum drying oven, and dry at 60°C for 12 h to obtain film A;

[0096] Step 3: Immerse the film A obtained in Step 2 in a DMSO / NaBH4 solution for 10 min, wherein the concentration of NaBH4 is 0.01 mol / L. -1 Afterwards, it was removed, rinsed three times with deionized water, and dried at 80°C for 20 minutes to form a PEDOT:PSS thermoelectric film B on the glass substrate. (The DMSO / NaBH4 solution is a mixed solution composed of dimethyl sulfoxide and sodium borohydride.)

[0097] Step 4: Add 200 μL of concentrated sulfuric acid to the film obtained in Step 3 on a heating stage at 180°C, keep it for 80 min, rinse it 4 times with deionized water, dry it at 80°C for 10 min, and then remove the glass substrate to obtain PEDOT:PSS flexible thermoelectric film C.

[0098] Example 12

[0099] Step 1: Clean the glass substrate in sequence with deionized water, acetone, and isopropanol, and then dry it;

[0100] Step 2: Drop-coat 300 μL of PEDOT:PSS aqueous solution (Clevious PH1000) onto the glass substrate obtained in Step 1, place it in a vacuum drying oven, and dry at 60°C for 12 h to obtain film A;

[0101] Step 3: Immerse the film A obtained in Step 2 in sodium sulfite solution for 30 minutes, then take it out, rinse it 3 times with deionized water, and dry it at 80°C for 20 minutes to form a PEDOT:PSS thermoelectric film B on the glass substrate.

[0102] Step 4: Add 300 μL of concentrated sulfuric acid to the film obtained in Step 3 on a heating stage at 160°C, keep it for 80 min, rinse it 4 times with deionized water, dry it at 80°C for 10 min, and then remove the glass substrate to obtain PEDOT:PSS flexible thermoelectric film C.

[0103] The present invention will now be described in further detail with reference to the accompanying drawings:

[0104] like Figure 1 As shown, the PEDOT:PSS film was first treated with a reducing solution (DMAC / H2O / LAA solution), followed by H2SO4 impregnation oxidation. (Hereinafter, treatment using only the first step is referred to as a one-step reduction treatment film, while treatment using the first step plus the second step of H2SO4 is referred to as a two-step reduction / oxidation treatment film.) With increasing H2SO4 treatment time, the conductivity gradually increased, indicating a higher degree of oxidation, but the crystallinity was not destroyed. Simultaneously, the Seebeck coefficient of the film decreased somewhat with increasing carrier concentration. After 60 min of H2SO4 treatment, the film's conductivity was 2626.9700 S / cm, the Seebeck coefficient was 17.0064 μV / K, and the maximum power factor was 75.9763 μW / m / K. 2 Compared to the film treated with a single reduction process, the film treated with a two-step reduction / oxidation process showed an improvement in thermoelectric performance of nearly 38%, demonstrating that the reduction / oxidation treatment of PEDOT:PSS can significantly improve thermoelectric performance.

[0105] like Figure 2 As shown, when the one-step reduction film is exposed to air for 15 days, the conductivity generally increases while the Seebeck coefficient decreases. After 15 days, the film's conductivity increases from 879.5 S / cm to 1015.7 S / cm, the Seebeck coefficient decreases from 25.2 μV / K to 19.7 μV / K, and the power factor increases from 55.9 μW / m / K. 2 Decreased to 39.6 μW / m / K 2 The oxidation level of PEDOT decreased by 29%. This is because the one-step reduction process causes the film to react with oxygen in the air, increasing the oxidation level of PEDOT and thus increasing the carrier concentration.

[0106] like Figure 3 As shown, when the two-step reduction / oxidation film (oxidation time 30 min) was exposed to air for 15 days, the conductivity was observed to increase steadily for the first 3 days, then decrease continuously until it stabilized at 1170 S cm on the 9th day. -1 Near the same location, the Seebeck coefficient exhibits the opposite change, first decreasing, then increasing, then decreasing slightly before reaching a steady state of 20.2 μV / K on day 12. Therefore, after 15 days of exposure to air, the power factor of the PEDOT:PSS film increases from 48.0909 μW / m / K. 2 It decreased to 47.9616 μW / m / K 2 It decreased by 0.02%, demonstrating good air stability.

[0107] like Figure 4 As shown, after exposing the two-step reduction / oxidation film (oxidation time of 60 min) to air for 7 days, the power factor of the PEDOT:PSS film decreased from 73.8267 to 53.9429, a decrease of 27%. This is different from the two-step reduction / oxidation film with an oxidation time of 30 min, showing poorer air stability.

[0108] like Figure 5 As shown, Raman spectroscopy was performed to further investigate its underlying mechanism. (1510cm) -1 The Raman peak at the specified location represents the degree of PEDOT oxidation. We can observe that, compared to the original PEDOT:PSS film, the Raman peak of the one-step reduction-treated film is more prominent, proving that the degree of PEDOT oxidation is reduced and the PEDOT carrier type changes from that of the original PEDOT. 2+ Convert to PEDOT + and PEDOT 0 At this point, the conductivity and Seebeck coefficient of the thin film are mainly determined by PEDOT. + and PEDOT 0 Dominated, while the film is exposed to air, PEDOT + and PEDOT 0 It readily reacts with oxygen, leading to a decrease in thermoelectric performance. The two-step reduction / oxidation treatment of the thin film (15-10 cm⁻¹) further exacerbates this. -1 The Raman peak becomes flat, mainly because after treatment with H2SO4, the H2SO4 molecules ionize into H3SO4. + and HSO4 - PSS ionized from PEDOT:PSS respectively - and PEDOT + Combined, doped ion PSS - The H2SO4 is removed, and an oxidation reaction occurs between H2SO4 and PEDOT, increasing the degree of PEDOT oxidation. PEDOT reaches a redox equilibrium, thus exhibiting relatively good stability in air. In contrast, the film treated with a two-step redox process for 60 minutes shows good stability at 1510 cm⁻¹. -1 The peak at the point becomes flatter, and due to over-oxidation, it is more susceptible to the influence of moisture in the air, causing its Seebeck coefficient to decrease. Therefore, we conclude that PEDOT:PSS films with a balanced oxidation / reduction level have excellent air stability, while both over-reduction and over-oxidation lead to a decrease in thermoelectric properties.

[0109] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a flexible PEDOT:PSS thermoelectric thin film with high thermoelectric performance and high air stability, characterized in that, This includes the following two methods: Method I: 1) PEDOT:PSS aqueous solution is uniformly dropped onto the substrate and dried to form a PEDOT:PSS film, resulting in film A; 2) Thin film A is soaked, drip-cast, or spin-coated with a reducing solution, and then rinsed to obtain thin film B; 3) Concentrated sulfuric acid was dropped onto the surface of film B under heating, rinsed, dried, and the substrate was removed to obtain PEDOT:PSS flexible thermoelectric film C; after treatment, PEDOT in the film was in an oxidation / reduction equilibrium state. Method II: 1) PEDOT:PSS aqueous solution is uniformly dropped onto the substrate and dried to form a PEDOT:PSS film, resulting in film A; 2) Thin film A is immersed, drop-cast, or spin-coated with a polar solvent, and then rinsed to obtain thin film D; 3) The film D is soaked, drip-cast, or spin-coated with a reducing solution, and then rinsed to obtain film E; 4) Concentrated sulfuric acid was dropped onto the surface of film E under heating, rinsed, dried, and the substrate was removed to obtain PEDOT:PSS flexible thermoelectric film F; after treatment, PEDOT in the film was in an oxidation / reduction equilibrium state.

2. The method for preparing a PEDOT:PSS flexible thermoelectric thin film with high thermoelectric performance and high air stability according to claim 1, characterized in that, In Method I and Method II, step 1), the substrate is first cleaned with deionized water, acetone and isopropanol in sequence, then dried, and then the PEDOT:PSS aqueous solution is evenly dropped onto the obtained substrate.

3. The method for preparing a PEDOT:PSS flexible thermoelectric thin film with high thermoelectric performance and high air stability according to claim 1, characterized in that, In Method I and Method II, the reducing solution is composed of a solution containing a reducing agent, including a solution composed of a reducing agent and deionized water, a solution composed of a polar solvent and a reducing agent, or a solution composed of a polar solvent, deionized water, and a reducing agent.

4. The method for preparing a PEDOT:PSS flexible thermoelectric thin film with high thermoelectric performance and high air stability according to claim 3, characterized in that, The reducing agent in the reducing solution is sodium hydroxide, sodium borohydride, sodium bicarbonate, sodium sulfite, hydrazine, or L-ascorbic acid.

5. The method for preparing a PEDOT:PSS flexible thermoelectric thin film with high thermoelectric performance and high air stability according to claim 1, characterized in that, In step 2) of Method II, the polar solvent is dimethyl sulfoxide, dimethylformamide, dimethylacetamide, ethylene glycol, or formamide.

6. The method for preparing a PEDOT:PSS flexible thermoelectric thin film with high thermoelectric performance and high air stability according to claim 1, characterized in that, In both Method I and Method II, the soaking time with a reducing solution is 10–60 min.

7. The method for preparing a PEDOT:PSS flexible thermoelectric thin film with high thermoelectric performance and high air stability according to claim 1, characterized in that, In both Method I and Method II, 100–300 μL of concentrated sulfuric acid is added dropwise, and the heating temperature is 120–180 °C for 10–80 min.

8. The method for preparing a PEDOT:PSS flexible thermoelectric thin film with high thermoelectric performance and high air stability according to claim 1, characterized in that, In both Method I and Method II, after rinsing with concentrated sulfuric acid, the product is dried at 60-80 °C for 10-20 min.

9. The PEDOT:PSS flexible thermoelectric film prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the PEDOT:PSS flexible thin film according to claim 9 in the fabrication of thermoelectric devices, optoelectronic devices and perovskite solar cells.

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