Thermoelectric thin film and preparation method and application thereof

Abstract

The invention discloses a thermoelectric film and a preparation method and application thereof. The method comprises the following steps: S1, mixing, heating and stirring a PBFDO solution and thermoplastic polyurethane, and performing centrifugal treatment to obtain a solution I; and S2, coating a mold with the solution I, and drying to obtain the thermoelectric thin film. According to the invention, the PBFDO solution is modified by thermoplastic polyurethane, so that the prepared thermoelectric film has good mechanical properties and thermoelectric properties.

Description

Technical Field

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

[0002] Thermoelectricity, also known as the thermoelectric conversion effect, is an emerging technology that can convert low-grade energy into high-grade energy. Since thermoelectric materials have the unique ability to convert thermal energy into electrical energy, they allow wearable electronic devices to collect energy when there is a temperature difference between the device and the environment, while providing temperature information proportional to the thermoelectric energy, continuously powering the sensor and performing continuous monitoring. When a thermoelectric device is attached to the human body, the connected skin can be regarded as a constant temperature heat source, which can establish a temperature difference with the other end of the device, namely the atmosphere. Based on this temperature difference, the thermoelectric device can perform the corresponding thermoelectric conversion, which can be used to power wearable electronic devices or as a sensor.

[0003] Thermoelectric materials are divided into organic and inorganic materials. Compared with inorganic thermoelectric materials, organic thermoelectric materials have natural advantages such as flexibility, easy processing, low thermal conductivity, and non-toxicity. Among them, P-type organic thermoelectric materials have developed rapidly, and their thermoelectric performance is close to that of inorganic materials. In contrast, the development of N-type materials lags far behind that of P-type materials. Although the carrier mobility of N-type materials is acceptable, their inherent carrier concentration is mostly low, so their thermal energy performance is generally low. Because of its low electron affinity (that is, the lowest occupied molecular orbital LUMO energy level is high), its stability is poor and it is difficult to meet the requirements of thermoelectric conversion. Recently, researchers have developed a new N-type organic thermoelectric material PBFDO with high thermoelectric performance. However, the mechanical properties of thin films prepared from pure PBFDO are very poor, which limits the development of its application.

[0004] Therefore, it is necessary to develop a new method for preparing thermoelectric thin 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 thermoelectric film, and the prepared thermoelectric film has excellent mechanical properties and thermoelectric properties.

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

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

[0008] A method for preparing a thermoelectric film according to a first aspect of the present invention comprises the following steps:

[0009] S1, mixing a PBFDO (polybenzofurandione) solution and a thermoplastic polyurethane, heating, stirring, and centrifuging to obtain a solution I;

[0010] S2. Coating the solution I on a mold and drying it to obtain a thermoelectric film.

[0011] The method for preparing the thermoelectric film according to the embodiment of the present invention has at least the following beneficial effects:

[0012] The present invention uses thermoplastic polyurethane to modify the PBFDO solution, so that the prepared thermoelectric film has good mechanical properties and thermoelectric properties. Furthermore, through centrifugal treatment, the mechanical properties and thermoelectric properties of the thermoelectric film can be further improved.

[0013] According to a preferred embodiment of the present invention, the mass percentage of the thermoplastic polyurethane in the solution I is 0.5% to 1.5% based on the total mass of the solution I. Thus, within the above range, while maintaining excellent thermoelectric properties, it also has higher mechanical properties.

[0014] According to a preferred embodiment of the present invention, based on the total mass of the solution I, the mass percentage of the thermoplastic polyurethane in the solution I is 0.5% to 1%.

[0015] According to a preferred embodiment of the present invention, the concentration of the PBFDO solution is 10-12 mg / mL.

[0016] According to a preferred embodiment of the present invention, the centrifugal rotation speed is 2000-4000 r / min.

[0017] According to a preferred embodiment of the present invention, the centrifugation time is 5 to 20 minutes.

[0018] According to a preferred embodiment of the present invention, the heating temperature is 40°C to 80°C.

[0019] According to a preferred embodiment of the present invention, the stirring speed is 600-1200 r / min.

[0020] According to a preferred embodiment of the present invention, the stirring time is 4 to 8 hours.

[0021] According to a preferred embodiment of the present invention, the drying temperature is 40-80°C.

[0022] According to a preferred embodiment of the present invention, the drying time is 8 to 16 hours.

[0023] A thermoelectric film provided according to a second aspect of the present invention is prepared by the preparation method described in the first aspect of the present invention.

[0024] A third aspect of the present invention provides an application of the above-mentioned thermoelectric film in a thermoelectric sensor or a thermoelectric generator.

[0025] 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

[0026] 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:

[0027] Figure 1 is a schematic flow chart of a method for preparing a thermoelectric film according to Example 1 of the present invention;

[0028] Figure 2 It is a schematic structural diagram of the thermoelectric generator of Example 4 of the present invention. DETAILED DESCRIPTION

[0029] 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.

[0030] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0031] The raw materials used in the examples and comparative examples of the present invention are as follows:

[0032] PBFDO solution: Dongguan Fuan Optoelectronics Technology Co., Ltd. (Cat. No.: LOT021430272-74-3, concentration: 10-12 mg / mL);

[0033] Thermoplastic polyurethane: BASF, Germany; Product No. 1180A;

[0034] Carboxymethyl cellulose (CMC): Guangzhou Xiaodi Biotechnology Co., Ltd. (brand: Yuanye Bio, product number: S14015-250g; 9004-32-4).

[0035] Example 1

[0036] This example provides a thermoelectric film, and the preparation method thereof is as follows:

[0037] S1. Take a 30 mL small bottle, add 29.85 g of PBFDO solution and 0.15 g of thermoplastic polyurethane, then put in a rotor, place it on a 60°C water bath and heat it on a magnetic stirrer and stir it for 6 hours until it is evenly stirred; after 6 hours, a uniformly mixed composite solution is obtained; the composite solution is centrifuged (at a speed of 3000 r / min for 5 minutes) to obtain solution I (the mass percentage of thermoplastic polyurethane in solution I is 0.5%);

[0038] S2. Pour solution I on a mold with a length × width of 20 cm × 5 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 thermoelectric film.

[0039] Example 2

[0040] This example provides a thermoelectric film, and the preparation method thereof is as follows:

[0041] S1. Take a 30 mL small bottle, add 29.7 g of PBFDO solution and 0.3 g of thermoplastic polyurethane, then put in a rotor, place it on a 60°C water bath and heat it on a magnetic stirrer and stir it for 6 hours until it is evenly stirred; after 6 hours, a uniformly mixed composite solution is obtained; the composite solution is centrifuged (at a speed of 3000 r / min for 5 minutes) to obtain a solution I (the mass percentage of thermoplastic polyurethane in solution I is 1%);

[0042] S2. Pour solution I on a mold with a length × width of 20 cm × 5 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 thermoelectric film.

[0043] Example 3

[0044] This example provides a thermoelectric film, and the preparation method thereof is as follows:

[0045] S1. Take a 30 mL small bottle, add 29.55 g of PBFDO solution and 0.45 g of thermoplastic polyurethane, then put in a rotor, place it on a 60°C water bath and heat it on a magnetic stirrer and stir it for 6 hours until it is evenly stirred; after 6 hours, a uniformly mixed composite solution is obtained; the composite solution is centrifuged (at a speed of 3000 r / min for 5 minutes) to obtain solution I (the mass percentage of thermoplastic polyurethane in solution I is 1.5%);

[0046] S2. Pour solution I on a mold with a length × width of 20 cm × 5 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 thermoelectric film.

[0047] Example 4

[0048] This example provides a thermoelectric generator using the thermoelectric film of Example 1 of the present invention as a material.

[0049] The thermoelectric film of Example 1 was cut into small rectangular films with a length of 2 cm and a width of 1 cm. Multiple small films were connected in series using commercial carbon fiber and silver glue to obtain a PBFDO thermoelectric generator; its structural schematic diagram is shown in FIG. Figure 2 As shown, the black square is the thermoelectric film of Example 1, the connecting wire is commercial carbon fiber, the black square is the substrate, one end is the hot end (red), and the other end is the cold end (blue).

[0050] Comparative Example 1

[0051] Comparative Example 1 provides a thermoelectric film, and its preparation method is the same as that of Example 1, except that ultrasonic treatment is not required.

[0052] Comparative Example 2

[0053] Comparative Example 1 provides a thermoelectric film, and its preparation method is the same as that of Example 1, except that CMC is used instead of thermoplastic polyurethane.

[0054] Comparative Example 3

[0055] Comparative Example 3 provides a thermoelectric film, and its preparation method is the same as that of Example 1, except that no thermoplastic polyurethane is added.

[0056] Performance Testing

[0057] The thermoelectric films of the embodiments of the present invention and the comparative examples were tested as follows: the test results are shown in Table 1.

[0058] Mechanical properties

[0059] Tensile properties (stress, strain and stress-strain curve): The film was cut into 3 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.

[0060] Electrical properties

[0061] Conductivity σ: After cutting the film into 3cm×1cm, 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. Conductivity is the reciprocal of resistivity, that is, σ=1 / ρ, where:

[0062] ρ is the resistivity, and its unit is ohm·meter (Ω·m).

[0063] R is the resistance of the conductor, measured in ohms (Ω).

[0064] A is the cross-sectional area of ​​the conductor, in square meters (m 2 ).

[0065] L is the length of the conductor in meters (m).

[0066] Seebeck coefficient S: Silver glue is applied to both ends of a 3cm×1cm film, and commercial carbon fibers are connected to each other. After the silver glue is dried, the two ends of the film are placed on a heating table and a constant temperature cold source (using a thermocouple for real-time temperature calibration), and the carbon fibers at both ends are connected to a nanovoltmeter for testing. The open circuit voltage at different temperatures is measured (△T-△V graph), and the slope obtained by fitting is the Seebeck coefficient S, in μV / K.

[0067] Power factor (PF): PF = σ·S 2 , where S represents the Seebeck coefficient and σ represents the conductivity.

[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 diagram).

[0069] Table 1 Examples 1 to 3 and Comparative Examples 1 to 2

[0070]

[0071] It can be seen from the thermoelectric performance data of Comparative Example 3 that without the additional addition of thermoplastic polyurethane, the prepared film has the disadvantages of being brittle and unable to be demolded, and has very poor mechanical properties, which makes it impossible to directly use it in practical applications.

[0072] From the data of Comparative Example 2, it can be seen that the addition of CMC will significantly reduce the Seebeck coefficient of the film, which indirectly leads to a significant decrease in the thermoelectric performance, while the introduction of TPU in the embodiment of the present invention will hardly affect the Seebeck coefficient of the film.

[0073] From the data of Comparative Example 1, it can be seen that the absence of ultrasound will reduce the uniformity of the solution, and the bubbles in the solution will cause more defective areas to appear in the film, thereby reducing the thermoelectric and mechanical properties of the film, resulting in a decrease in its overall performance.

[0074] From the data of Examples 1 to 3 of the present invention, it can be seen that Examples 1 to 3 have good electrical conductivity and mechanical properties and high comprehensive performance.

[0075] 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 raw materials and process of film preparation will not cause pollution to the environment, it is an environmentally friendly material.

[0076] The present invention uses the novel organic thermoelectric material PBFDO as a raw material to prepare a self-supporting thermoelectric film, and its good thermoelectric performance and mechanical properties are helpful to promote the development of the N-type organic thermoelectric application field.

[0077] 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 thermoelectric film, characterized in that: The steps include: S1, mixing the PBFDO solution and thermoplastic polyurethane, heating, stirring, and centrifuging to obtain a solution I; S2. Coating the solution I on a mold and drying it to obtain a thermoelectric film.

2. The method for preparing a thermoelectric film according to claim 1, characterized in that: Calculated based on the total mass of solution I, the mass percentage of the thermoplastic polyurethane in solution I is 0.5% to 1.5%.

3. The method for preparing a thermoelectric film according to claim 1, characterized in that: The centrifugal speed is 2000-4000 r / min.

4. The method for preparing a thermoelectric thin film according to claim 1, characterized in that: The centrifugation time is 5 to 20 minutes.

5. The method for preparing a thermoelectric thin film according to claim 1, characterized in that: The stirring speed is 600-1200 r / min.

6. The method for preparing a thermoelectric thin film according to claim 1, characterized in that: The stirring time is 4 to 8 hours.

7. The method for preparing a thermoelectric thin film according to claim 1, characterized in that: The drying temperature is 40-80°C.

8. The method for preparing a thermoelectric thin film according to claim 1, characterized in that: The drying time is 8 to 16 hours.

9. A 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 thermoelectric film according to claim 9 in a thermoelectric sensor or a thermoelectric generator.

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