Ferroelectric-assisted high-performance triboelectric nanogenerators based on electrospun P(VDF-TrFE) composite nanofibers with barium titanate nanofillers

Triboelectric nanogenerators (TENGs) are flexible, efficient, and cost-effective energy harvesters. Here, we develop high-performance ferroelectric-assisted TENGs using electrospun fibrous surfaces based on P(VDF-TrFE) with dispersed BaTiO3 (BTO) nanofillers in either cubic (CBTO) or tetragonal (TBTO) form. TENGs with three types of tribo-negative surface (pristine P(VDF-TrFE), P(VDF-TrFE)/CBTO and P(VDF-TrFE)/TBTO) in contact with PET were investigated and output increased progressively from pristine (0.75 W/m2) to CBTO (2 W/m2) and to TBTO (2.75 W/m2). Accounting for contact pressure, the max output (Voc = 315 V & Jsc = 6.7 µA/cm2) is significantly higher than for TENGs having spin-coated P(VDF-TrFE)/BTO. It is hypothesized that electrospinning increases dipole alignment due to high applied voltages, but also aids the formation of a highly oriented crystalline β-phase via uniaxial stretching. Essentially, tribo-charge transfer is boosted due to increased surface potential owing to enhanced ferroelectric polarization. P(VDF-TrFE)/TBTO produced higher output than P(VDF-TrFE)/CBTO even though permittivity is nearly identical. Thus, it is shown that BTO fillers boost output, not just by increasing permittivity, but also by enhancing the crystallinity and amount of the β-phase (as TBTO produced a more crystalline β-phase present in greater amounts). Finally, the ferroelectric-assisted TENG was integrated with a flexible graphene electrode-based supercapacitor to produce a self-charging system capable of charging to 1.25 V in just 5 min. These results demonstrate that this technology can be valuable in wearable applications where higher power output, more efficient charging and flexibility are paramount.