Fabrication of n -type flexible films with a double-layer structure by hybridizing Bi 2 Se 3 and polyvinyl alcohol)
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Research Letter
Fabrication of n-type flexible films with a double-layer structure by hybridizing Bi2Se3 and poly(vinyl alcohol) Akira Ohnuma, New Field Pioneering Division, Toyota Boshoku Corporation, Kariya, Aichi 448-8651, Japan Address all correspondence to Akira Ohnuma at [email protected] (Received 18 April 2018; accepted 3 July 2018)
Abstract Here we report a new type of n-type flexible film with a double-layer structure fabricated by hybridizing an n-type inorganic thermoelectric material, bismuth selenide (Bi2Se3), and an ordinary insulating polymer, poly(vinyl alcohol) (PVA). Flake-shaped Bi2Se3 nanoparticles (Bi2Se3 nanoflakes) modified with/without gold (Au) nanoparticles were distributed in the one side of PVA film with the particular arrangement, and the hybrid film showed a high Seebeck coefficient (−91 µV/K at room temperature) as an n-type flexible material. Our method is expected to be used for the design of flexible functional devices such as flexible thermoelectric modules.
Introduction Since two-thirds of chemical energy from fossil fuels have been exhausted as heat energy without use, much attention has been paid to thermoelectric technology which can convert heat energy into electric energy and vice versa.[1,2] The performance of thermoelectric materials is determined by a dimensionless figure of merit, ZT, which is defined as σS2 T/κ, where σ is the electrical conductivity, S is the Seebeck coefficient, T is the absolute temperature, κ is the thermal conductivity, and σS2 represents the power factor. Materials are required to have a higher power factor and lower thermal conductivity to gain a higher ZT value.[3,4] Inorganic thermoelectric materials such as bismuth telluride (Bi2Te3) and bismuth selenide (Bi2Se3) have been investigated intensively and developed for commercial applications at room temperature.[5–8] Despite the high-power factor and figure of merit, inorganic materials have several disadvantages such as difficulty in the mass production of devices due to their poor formability. Increasing attention has been paid to organic thermoelectric materials because of their various advantages over inorganic thermoelectric materials. Especially, their flexibility enables us to set thermoelectric materials easily on any surface with shapes of variety, and also their low thermal conductivity is attractive to achieve a better thermoelectric property. Although conductive polymers like poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) are promising p-type flexible thermoelectric materials,[4,9,10] it is still not easy to use them for mass production due to the higher prices compared with ordinary polymers (i.e., insulating polymers). Furthermore, the development of n-type flexible materials is desirable for the design of
π-shaped thermoelectric modules in which thermoelectric couples that consist of n-type (containing free electrons) and p-type (containing free holes) thermoelectric elements are connected electrically in series and thermally in parallel,[6,11,12] but there has be
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