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Research progress of flexible organic/inorganic thermoelectric composite materials where Shanghai Silicate is located
[ Instrument R&D of Instrumentation Network ] Flexible thermoelectric energy conversion technology can convert the environment or human body temperature difference into electrical energy to realize the self-power supply of electronic devices, and has broad application prospects in wearable and other fields. Traditional inorganic thermoelectric materials have excellent thermoelectric properties, but do not have flexible functions; while organic thermoelectric materials have good flexibility and bending properties, but the thermoelectric properties are extremely low. Organic/inorganic composite thermoelectric materials can integrate the thermoelectric performance of inorganic materials and the good bending properties of organic materials, and have become a research hotspot in recent years. Carbon nanotubes or metal nanowires with a one-dimensional structure can form a tightly connected conductive network with one-dimensional molecular chains of organic materials, and provide highly conductive channels along the chain network, so they are often used in organic/inorganic composite thermoelectric materials. . However, the extremely low Zebeck coefficient of carbon nanotubes or metal nanowires makes it difficult to increase the Zebeck coefficient of composite materials. Although the inorganic thermoelectric material has a high Zebeck coefficient, its shape is usually in the form of flakes or particles, resulting in low electrical transport performance of the composite material. Therefore, how to select matching organic/inorganic materials to obtain good electrical transport has become a key scientific issue in the research of organic/inorganic composite thermoelectric materials.
Recently, Shi Xun, Chen Lidong, Associate Researchers Qiu Pengfei, Qu Sanyin, etc., researchers at the Shanghai Institute of Ceramics, Chinese Academy of Sciences, and He Jian, a professor at Clemson University in the United States, proposed a new dimension matching thermoelectric composite design strategy That is, using inorganic semiconductor materials with the same one-dimensional structure to prepare high-performance PVDF/Ta4SiTe4 organic/inorganic flexible thermoelectric composite films, the normalized maximum power density of the prototype device at a temperature difference of 35.5K is the highest among the currently reported flexible thermoelectric devices. value. Related research results are published in Energy & Environmental Science under the title of Conformal organic–inorganic semiconductor composites for flexible thermoelectrics.
The organic material polyvinylidene fluoride (PVDF) has a one-dimensional chain structure and is an insulator with excellent flexibility. Based on the design idea of ​​dimensional matching, the team chose Ta4SiTe4 inorganic material which also has a one-dimensional structure and PVDF to prepare an organic/inorganic flexible composite film. Through the chemical vapor transport reaction, Ta4SiTe4 one-dimensional whiskers doped with 0.5% Mo in the Ta site were obtained. Then, using N,N-dimethylformamide (DMF) as a dispersant, a PVDF/Ta4SiTe4 composite film was obtained by the method of drop coating. Scanning electron microscopy found that Ta4SiTe4 whiskers were evenly dispersed in the PVDF matrix to form a network structure. Transmission electron microscopy showed that Ta4SiTe4 whiskers and PVDF formed a tightly bonded two-phase interface. The thermoelectric performance characterization found that PVDF/50 wt% Ta4SiTe4 has excellent electrical transport performance, with a power factor as high as 1060 μWm-1K-2 at 220 K. In particular, at the same conductivity, the Zebeck coefficient of PVDF/50 wt% Ta4SiTe4 film is much higher than that of organic/inorganic composite films based on carbon nanotubes or metal nanowires. Ta4SiTe4's own semiconductor transport characteristics and one-dimensional structure jointly produce the above-mentioned excellent electrical transport performance.
While achieving excellent electrical transport performance, the organic/inorganic composite film formed by dimensionally matched PVDF and Ta4SiTe4 also has good flexibility. After repeated bending 5000 times on a curved surface with a diameter of 9 mm, the PVDF/50 wt% Ta4SiTe4 film resistance did not change significantly. The research team preliminarily prepared a prototype thermoelectric device containing 4 PVDF/50 wt% Ta4SiTe4 thermocouples. At a temperature difference of 35.5K, the normalized maximum power density of the device reached 0.13 Wm-1, which is the current reported flexible thermoelectric device. The maximum value.
The research work has received funding and support from the National Key R&D Project, the National Natural Science Foundation of China, the Youth Innovation Promotion Association of the Chinese Academy of Sciences, and the Shanghai Youth Science and Technology Star Project.