Flexible textile thermoelectric materials with CuI nanostructured films deposited on composites of nanocellulose and polyester fabric

In this work, nanocomposites of polyester fabric and biopolymer nanocellulose were developed as a textile backing for an efficient thermoelectric (TE) textile material with a nanostructured semiconductor film of copper iodide (CuI) 5 μm thick. Among the three methods for obtaining nanocellulose hydrogel from hemp organosolv pulp, thermochemical treatment with deep eutectic solvent turned out to be the best. This nanocellulose is composed of rod-shaped cellulose nanocrystals, which provide strength to the nanocomposite so that the TE textile sample does not crack. The CuI film in this thermoelectric textile has the best crystal structure, is non-stoichiometric, enriched in iodine, and has copper vacancies, which contributes to a large Seebeck coefficient and low resistivity, which ensures an increase in thermoelectric efficiency. The thermal image of the TE textile confirms the low thermal conductivity of the nanocomposite. Their maximum specific output power 15.6 $\mu \mathrm{W}/\text{cm}^{2}$ is one of the best among modern solid-state miniature, flexible and textile thermoelectric materials.