Flexible Environmentally Friendly Thermoelectric Material Made of Copper (1) Iodide and Nanocellulose for Green Energy

Authors N.P. Klochko1 , V.A. Barbash2, S.I. Petrushenko3,4, V.R. Kopach1 , Y.M.  Shepotko1, S.V. Dukarov3, V.M. Sukhov3, O.V. Yashchenko2, A.L. Khrypunova1

1National Technical University “Kharkiv Polytechnic Institute”, 2 Kyrpychova st., 61002 Kharkiv, Ukraine

2National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, 37 Peremohy prosp., 03056 Kyiv, Ukraine

3V.N. Karazin Kharkiv National University, 4, Svobody sq., 61022 Kharkiv, Ukraine

4Institute for Nanomaterials, Advanced Technologies and Innovation, Technical University of Liberec, Liberec, Czech Republic

Issue Volume 15, Year 2023, Number 4
Dates Received 12 May 2023; revised manuscript received 16 August 2023; published online 30 August 2023
Citation N.P. Klochko, V.A. Barbash, S.I. Petrushenko, и др., J. Nano- Electron. Phys. 15 No 4, 04003 (2023)
DOI https://doi.org/10.21272/jnep.15(4).04003
PACS Number(s) 73.50.Lw
Keywords Thermoelectric element, Thin film (101) , Nanocellulose, SILAR (6) , CuI (11) .

Herein, we have developed a new efficient flexible hydrophobic thermoelectric (TE) material with increased thermal stability and mechanical strength for green energy production. The 8 µm thick flexible nanocellulose (NC) substrate was obtained from stalks of common reed by TEMPO-mediated oxidation. It has a high crystallinity index of 88 % and the amount of coherent scattering of nanocrystals in the range from 2 to 3 nm. A CuI film with a thickness of 4.3 μm was deposited on the NC substrate by the Successive Ionic Layer Adsorption and Reaction (SILAR), and thus a CuI/NC thin film thermoelectric material was obtained. The average size of the CuI coherent scattering regions is 25 nm. CuI nanocrystals contain dislocations (1.6x1015 lines/m2) and tensile microstrains of 6x103 arb. units. The optical band gap Eg for direct allowed transitions in the CuI film is about 3.0 eV. The high hydrophobicity of the CuI/NC material is a useful feature for applications in humid environments. The CuI/NC material contains the same number of copper and iodine atoms. In addition, a small amount of sulfur (<1 at.%) is present in the copper iodide film, which increases the thermopower coefficient of CuI/NC to 6.7 μW/(m·K2) at T = 340 K. Its positive Seebeck coefficient S = 108 μV/K confirmed the p-type conductivity of CuI. The change in the resistivity upon initial heating and subsequent cooling demonstrated the electrical conductivity crossover typical of films of nanocrystalline degenerate semiconductor CuI. A CuI/NC sample in the form of a 3 cm x 1 cm strip was tested as a planar thin film TE element. The output power density of a CuI/NC TE element 0.123 W/m2 was experimentally recorded at a difference between its hot and cold edges of 40 K.

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