Highly Efficient 3D-Printed PVDF-Based Triboelectric Nanogenerators Featuring Polymorphic Perovskite Nanofillers

The realization of optimal performance in polyvinylidene fluoride (PVDF)-based triboelectric nanogenerators (TENGs) is fundamentally linked to the enhancement of the β-phase content of PVDF (β-PVDF), which is crucial for improving dielectric properties and surface charge density. Among various strategies, the incorporation of semiconducting perovskite nanofillers has been particularly effective in achieving the desired β-PVDF phase for TENG applications. Herein, PVDF dielectric films are embedded with polymorphic formamidinium lead triiodide (FAPbI₃) perovskite nanofillers and fabricated using a cost-effective 3D direct-ink writing setup. The phase transformation of FAPbI₃ nanofillers within the PVDF matrix, in response to varying annealing temperatures, resulted in the formation of PVDF-FAPbI₃(δ) and PVDF-FAPbI₃(α) composite films, each exhibiting distinct morphology and dielectric characteristics. The incorporation of δ-FAPbI₃ nanofillers rendered the composite film porous and increased the β-PVDF content from ≈45% to ≈83%. By converting the δ-FAPbI₃ into the α-FAPbI₃ through post-annealing, the composite film transitioned into a mesoporous structure with enhanced tribo-positive properties. This modification substantially improved the output performance of the TENG, achieving a peak-to-peak voltage (V_p-p) of 392 Vand a power density of 2587 µW cm⁻². This work highlights the significant impact of perovskite polymorphism on the performance of TENG devices.