Nonwoven Polymeric Nanofiber Sheets: Path Forward Toward a New Class of Hybrid Flexible Thermoelectrics

Hybrid flexible thermoelectric (TE) materials are widely being explored for wearable TEs, micro power generators, and self-powered electronics. The commonly used methods for developing hybrid flexible TE materials are organic–inorganic composite which exhibits low TE performance and second is inorganic material deposition over organic substrate making it a two-sheet structure that has sustainability concerns. In view of this, herein, a different class of highly flexible hybrid TE materials are designed using a network of electrospun 1D nanofibers (NFs) as a substrate which provides high surface area, better connectivity, and high flexibility. For the proof of concept, the NFs sheets of two polymers polyacrylonitrile (PAN) and cellulose acetate are used to deposit the well-known Bi2Te3 as a case study. Herein, the directionally aligned PAN-based NFs sheet exhibits good TE properties leading to the maximum PF ≈51.4 μW m−1 K−2 at 384 K for the P-400 sample. Herein, the concept of a new class of hybrid TEs is successfully demonstrated by utilizing the flexible NF sheet as a substrate for inorganic TE materials, which will pave the way for sustainable flexible TE. Further, the TE performance can be enhanced by modulating certain factors such as the synthesis conditions of NFs and inorganic material, the thickness of deposition, and so on.