Self-supporting thermoelectric thin film and preparation method and application thereof

Abstract

The invention discloses a self-supporting thermoelectric thin film and a preparation method and application thereof. The preparation method of the self-supporting thermoelectric thin film comprises the following steps: S1, mixing a PEDOT: PSS solution and DMSO to obtain a solution I; mixing the solution I and hydroxyethyl cellulose, and performing ultrasonic treatment to obtain a solution II; and S2, coating a mold with the solution II, and drying to obtain the self-supporting thermoelectric thin film. The PEDOT: PSS solution is used as a main material, the thermoelectric performance and the mechanical performance of the PEDOT: PSS solution are enhanced through DMSO and hydroxyethyl cellulose respectively, and the prepared film is good in mechanical performance and high in cycling stability; and the thermoelectric performance is high.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric films, and in particular to a self-supporting thermoelectric film and a preparation method and application thereof. Background Art

[0002] Excellent thermoelectric materials should have high electrical conductivity, low thermal conductivity, and excellent mechanical properties. Compared with inorganic thermoelectric materials, organic thermoelectric materials started later, but organic thermoelectric materials have the advantages of easy processing, light weight, natural non-toxicity, and low thermal conductivity. And the cost is lower, making the application of organic thermoelectric materials more extensive.

[0003] Among the current organic thermoelectric materials, the development of P-type organic thermoelectric materials is ahead of that of N-type organic thermoelectric materials, and they have excellent stability in the air. Although they have excellent thermoelectric performance, most of the films made of organic thermoelectric materials are not only poorly flexible but also often cannot stand independently, which makes it difficult to apply them to flexible-based applications such as wearables.

[0004] Therefore, it is necessary to develop a method for preparing self-supporting thermoelectric films. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the first aspect of the present invention provides a method for preparing a self-supporting thermoelectric film, wherein the self-supporting thermoelectric film prepared by the method has excellent mechanical properties and thermoelectric properties.

[0006] The second aspect of the present invention also provides a self-supporting thermoelectric film.

[0007] The third aspect of the present invention also provides an application of a self-supporting thermoelectric film.

[0008] According to a first aspect of the present invention, a method for preparing a self-supporting thermoelectric film is provided, comprising the following steps:

[0009] S1. PEDOT:PSS solution and DMSO are mixed to obtain solution I; solution I and hydroxyethyl cellulose are mixed and ultrasonicated to obtain solution II;

[0010] S2. Coat solution II on a mold and dry it to obtain a self-supporting thermoelectric film.

[0011] The method for preparing a self-supporting thermoelectric film provided in accordance with an embodiment of the present invention has at least the following beneficial effects:

[0012] The present invention uses PEDOT:PSS solution as the main material, and uses DMSO and hydroxyethyl cellulose to respectively enhance the thermoelectric performance and mechanical performance thereof, so that the prepared film has the characteristics of good mechanical performance, high cycle stability and high thermoelectric performance.

[0013] According to a preferred embodiment of the present invention, the mass percentage of the hydroxyethyl cellulose is 0.05-0.2% based on the total mass of solution II. Thus, when the mass percentage of the hydroxyethyl cellulose is 0.05-0.2%, the prepared film has good mechanical properties.

[0014] According to a preferred embodiment of the present invention, the mass percentage of the hydroxyethyl cellulose is 0.1-0.15% based on the total mass of solution II. Thus, when the content of hydroxyethyl cellulose is within the above range, the mechanical properties are improved and the influence on the thermoelectric properties is reduced.

[0015] According to a preferred embodiment of the present invention, the volume fraction of DMSO is 1% to 8% based on the total volume of the PEDOT:PSS solution. Thus, DMSO can further improve the conductivity of the film.

[0016] According to a preferred embodiment of the present invention, the frequency of the ultrasound is 20 to 40 kHz, thereby achieving a better dispersion effect.

[0017] According to a preferred embodiment of the present invention, the ultrasonication time is 0.5 to 3 hours.

[0018] According to a preferred embodiment of the present invention, in step S2, the drying temperature is 50-80°C.

[0019] According to a preferred embodiment of the present invention, in step S2, the drying time is 8 to 24 hours.

[0020] According to a second aspect of the present invention, there is provided a self-supporting thermoelectric film, which is prepared by the preparation method described in the first aspect of the present invention.

[0021] A third aspect of the present invention provides a use of the self-supporting thermoelectric film described above in a thermocouple or a thermoelectric generator.

[0022] Other features and advantages of the present invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0024] Figure 1 is a schematic structural diagram of a thermoelectric generator provided in Example 1 of the present invention;

[0025] Figure 2It is a schematic diagram of the structure of the thermocouple temperature sensor provided by the present invention;

[0026] Figure 3 is a schematic diagram showing the change in resistance of the self-supporting thermoelectric film according to Example 1 of the present invention as the number of bending times increases;

[0027] Figure 4 This is a test data diagram of the open circuit voltage and output voltage of the thermoelectric generator provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0029] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0030] Some of the raw materials in the examples and comparative examples of the present invention are as follows:

[0031] PEDOT:PSS solution: Xi'an Yuri Solar Energy Technology Co., Ltd. (brand: Xi'an Baolait (p-oled) item number: 306021-100ML 155090-83-8 concentration: 1-1.3wt%);

[0032] Hydroxyethyl cellulose; Guangzhou Ximi Biotechnology Co., Ltd. (Brand: Yuanye Biotechnology; Product No.: S14169-250g; 9004-62-0; Concentration: high viscosity, 38000-42000mpas);

[0033] Carboxymethyl cellulose: Guangzhou Xiaodi Biotechnology Co., Ltd. (brand: Yuanye Bio, product number: S14015-250g; 9004-32-4 concentration: column chromatography).

[0034] Example 1

[0035] This example provides a self-supporting thermoelectric film, and the preparation method thereof is as follows:

[0036] S1. 9.485 g of PEDOT:PSS solution and DMSO (volume fraction 5%; 0.5 g) were mixed to obtain solution I. Solution I and hydroxyethyl cellulose (0.015 g) were mixed and stirred and ultrasonicated (frequency 40 kHz) Z , temperature is 25° C., time is 1 h) to obtain solution II; wherein the mass percentage of hydroxyethyl cellulose is 0.15%;

[0037] S2. Pour solution II on a mold with a length × width of 30 cm × 6 cm and a thickness of 1 mm, and brush it evenly; place the mold in an oven at 60°C and dry it for 12 hours to completely evaporate the solvent, thereby obtaining a self-supporting thermoelectric film (the film thickness is about 40 μm).

[0038] Example 2

[0039] This example provides a self-supporting thermoelectric film, and the preparation method thereof is as follows:

[0040] S1. 9.495 g of PEDOT:PSS solution and 5% by volume of DMSO (0.5 g) were mixed to obtain solution I; solution I and hydroxyethyl cellulose (0.005 g) were mixed and stirred and ultrasonicated (frequency of 40 kHz, temperature of 25° C., time of 1 h) to obtain solution II; wherein the mass percentage of hydroxyethyl cellulose was 0.05%;

[0041] S2. Pour solution II on a mold with a length × width of 30 cm × 6 cm and a thickness of 1 mm, and brush it evenly; place the mold in an oven at 60°C and dry it for 12 hours to completely evaporate the solvent, thereby obtaining a self-supporting thermoelectric film (the film thickness is about 40 μm).

[0042] Example 3

[0043] This example provides a self-supporting thermoelectric film, and the preparation method thereof is as follows:

[0044] S1. 9.490 g of PEDOT:PSS solution and 5% by volume of DMSO (0.5 g) were mixed to obtain solution I; solution I and hydroxyethyl cellulose (0.010 g) were mixed and stirred and ultrasonicated (frequency of 40 kHz, temperature of 25° C., time of 1 h) to obtain solution II; wherein the mass percentage of hydroxyethyl cellulose was 0.1%;

[0045] S2. Pour solution II on a mold with a length × width of 30 cm × 6 cm and a thickness of 1 mm, and brush it evenly; place the mold in an oven at 60°C and dry it for 12 hours to completely evaporate the solvent, thereby obtaining a self-supporting thermoelectric film (the film thickness is about 40 μm).

[0046] Example 4

[0047] This example provides a self-supporting thermoelectric film, and the preparation method thereof is as follows:

[0048] S1. 9.480 g of PEDOT:PSS solution and 5% by volume of DMSO (0.5 g) were mixed to obtain solution I; solution I and hydroxyethyl cellulose (0.020 g) were mixed and stirred and ultrasonicated (frequency of 40 kHz, temperature of 25° C., time of 1 h) to obtain solution II; wherein the mass percentage of hydroxyethyl cellulose was 0.2%;

[0049] S2. Pour solution II on a mold with a length × width of 30 cm × 6 cm and a thickness of 1 mm, and brush it evenly; place the mold in an oven at 60°C and dry it for 12 hours to completely evaporate the solvent, thereby obtaining a self-supporting thermoelectric film (the film thickness is about 40 μm).

[0050] Comparative Example 1

[0051] The comparative example provides a self-supporting thermoelectric film, and the preparation method thereof is substantially the same as that of Example 1, except that carboxymethyl cellulose (CMC) is used instead of hydroxyethyl cellulose (EHC) in Example 1.

[0052] Example 5

[0053] This example provides a thermoelectric generator, and the preparation steps are as follows:

[0054] The self-supporting thermoelectric film prepared in Example 1 of the present invention is used as a P-type film;

[0055] Using cotton cloth as the base material, the obtained P-type film was cut into a "fiber" film with a length of 2 cm and a width of 0.3 cm. Commercial carbon fiber was used as the conductor and silver glue was used as the adhesive. The P-type film was connected in series through the carbon fiber and the whole was bonded to the base material. After standing at room temperature for 2-3 hours, a thermoelectric energy harvesting device was obtained.

[0056] Its structural diagram is as follows Figure 1 As shown; the blue square is a P-type film, the black curved thick line is commercial carbon fiber [the carbon fiber is bonded to both ends of the film using silver glue (gray)], the black square is the base material, one end is the hot end (red), and the other end is the cold end (blue).

[0057] Performance Testing

[0058] The self-supporting thermoelectric films of Examples 1 to 4 of the present invention and Comparative Example 1 were tested for electrical conductivity, tensile properties and Seebeck coefficient S in sequence; the results are shown in Table 1.

[0059] Conductivity: After cutting the film into 3cm×1cm pieces, place the multimeter's test pen at both ends of the film. When the reading is stable, record the reading (measure resistance). Calculate the resistivity according to the formula ρ=R×A / L. The conductivity is the reciprocal of the resistivity, that is, σ=1 / ρ, where:

[0060] ρ is the resistivity, and its unit is ohm·meter (Ω·m).

[0061] R is the resistance of the conductor, measured in ohms (Ω).

[0062] A is the cross-sectional area of ​​the conductor, in square meters (m 2 ).

[0063] L is the length of the conductor in meters (m).

[0064] Tensile properties (stress, strain and stress-strain curve): The film was cut into 5 cm × 1 cm, and both ends of the film were clamped with a universal material testing machine. The test was performed according to GB 13022-1991, and the tensile speed was 1 mm / min.

[0065] Seebeck coefficient S: The self-supporting thermoelectric films of Examples 1 to 4 of the present invention are prepared into thermocouple temperature sensors, the structural schematic diagram of which is shown in FIG. Figure 2 As shown, the specific steps are as follows:

[0066] The self-supporting thermoelectric films of Examples 1 to 4 of the present invention are used as P-type films; the obtained P-type films are cut into "fiber"-shaped films with a length of 2 cm and a width of 0.3 cm, and then one end of the film is bonded to a carbon fiber (black thick wire) using silver glue to form a thermocouple;

[0067] The hot end (working end) of the thermocouple is fixed on a temperature-controllable heating device, and the cold end (reference end) is placed on a constant temperature device (preferably room temperature). The hot end temperature is recorded as T 1 , the cold end temperature is recorded as T 0 , the hot end temperature is from T 0 Start heating up, record the voltage change across the thermocouple during the heating process, and obtain the △T-△V heating curve. Finally, calculate the slope of the curve to obtain the accurate Seebeck coefficient S of the material in μV / K.

[0068] Comprehensive performance: The calculation formula is = power factor (PF) × area of ​​stress-strain diagram (the area represents the total energy that the material can absorb before failure, and the area of ​​the stress-strain diagram is obtained by integrating the stress-strain diagram). The calculation formula of power factor (PF) is as follows: PF = S^2*σ. S represents the Seebeck coefficient, and σ represents the conductivity.

[0069] Table 1 Examples 1 to 4 and Comparative Example 1

[0070]

[0071] From the data in Table 1, it can be seen that the introduction of CMC has certain advantages in mechanical properties, but HEC is significantly ahead in electrical properties. In addition, when the amount of HEC used in the present invention is between 0.1% and 0.15%, it has better electrical conductivity and mechanical properties, and better comprehensive performance.

[0072] The method for preparing the self-supporting thermoelectric film proposed in the present invention is not only simple in process, but also low in cost and high in efficiency. While ensuring excellent thermoelectric performance, it also takes into account excellent mechanical properties. Moreover, since the material itself contains only organic components, it is green and degradable, and is an environmentally friendly material.

[0073] Furthermore, the self-supporting thermoelectric film of Example 1 of the present invention was subjected to a cyclic bending test (bending angle of 90 degrees, rotation speed of 20 degrees / s), and the results are as follows: Figure 3 As shown, in the 1000-cycle bending test, the resistivity change of the film is less than 0.5% (R / R0), which has good cycle performance.

[0074] Furthermore, the self-supporting thermoelectric film of Example 1 of the present invention was tested for output voltage; the results are as follows: Figure 4 As shown, Figure 4 a is the open circuit voltage (output voltage without external resistance) of the thermoelectric generator (device composed of P-type thin film); the potential difference gradually increases with the increase of temperature difference, and is close to a directly proportional relationship. For every 5K temperature difference, the potential difference across the thermoelectric device increases by 4mV. Figure 4 b is the output voltage of the thermoelectric generator under different external resistances; the closer the resistance value of the external resistor is to the device resistance value, the greater the output voltage. This result represents the output power in practical applications, that is, the output voltage of the thermoelectric generator prepared by P-type thin film series under the condition of external resistance of 100Ω-1MΩ, and the output voltage under open circuit. This effect has guiding significance for practical applications.

[0075] The above is a detailed description of the embodiments of the present invention, but the present invention is not limited to the above embodiments. Various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A method for preparing a self-supporting thermoelectric film, characterized in that: The steps include: S1. PEDOT:PSS solution and DMSO are mixed to obtain solution I; solution I and hydroxyethyl cellulose are mixed and ultrasonicated to obtain solution II; S2. Coat solution II on a mold and dry it to obtain a self-supporting thermoelectric film.

2. The method for preparing a self-supporting thermoelectric film according to claim 1, characterized in that: Calculated based on the total mass of solution II, the mass percentage of the hydroxyethyl cellulose is 0.05-0.2%.

3. The method for preparing a self-supporting thermoelectric film according to claim 1 or 2, characterized in that: Calculated based on the total mass of solution II, the mass percentage of the hydroxyethyl cellulose is 0.1-0.15%.

4. The method for preparing a self-supporting thermoelectric film according to claim 1, characterized in that: Calculated based on the total volume of the PEDOT:PSS solution, the volume fraction of the DMSO is 1% to 8%.

5. The method for preparing a self-supporting thermoelectric film according to claim 1, characterized in that: The frequency of the ultrasound is 20-40 kHz.

6. The method for preparing a self-supporting thermoelectric film according to claim 1, characterized in that: The ultrasonic time is 0.5 to 3 hours.

7. The method for preparing a self-supporting thermoelectric film according to claim 1, characterized in that: In step S2, the drying temperature is 50-80°C.

8. The method for preparing a self-supporting thermoelectric film according to claim 1, characterized in that: In step S2, the drying time is 8 to 24 hours.

9. A self-supporting thermoelectric film, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the self-supporting thermoelectric film according to claim 9 in a thermocouple or a thermoelectric generator.

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