Flexible Thermoelectric and Piezoelectric Hybrid Energy harvester by Adopting a Multifunctional Cellulose-based Composite Film

Thermoelectric (TE) and piezoelectric (PE) energy harvesting are the most advantageous conversion mechanisms for converting energy generated by the human body into electrical energy, respectively. However, the development of a hybrid energy harvester is essential for achieving high energy conversion efficiency since a single energy harvester cannot convert enough energy. Herein, we present a flexible TE-PE hybrid energy harvester (f-TPHEH) based on a self-assembled single film consisting of Bi2Te2.7Sn0.3 particles, BaTiO3 nanoparticles, and cellulose. The fabricated f-TPHEH exhibited a maximum TE output power of 18.47 nW and a PE instantaneous output of 13.5 nW under integrated thermal and bending conditions (ΔT = 40 K, bending displacement = 7 mm). We conducted a theoretical analysis using multiphysics simulation based on finite element analysis to support the experimental measurements of the fabricated f-TPHEH. In addition, to demonstrate the mechanical stability of the cellulose matrix-based f-TPHEH, a durability test was performed up to 5,000 cycles of bending deformation. This study presents a method for developing the flexible hybrid energy harvester using a low-cost and simple fabrication process.