Enhanced Piezoelectric Energy Harvester by Employing Freestanding Single-Crystal BaTiO₃ Films in PVDF-TrFE Based Composites

Advancements in wearable electronics and Internet of Things (IoT) sensors have catalyzed the need for effective micro-energy harvesting. Piezoelectric nanogenerators (PENGs) are ideal due to their high conversion efficiency and durability. However, the contrast between the high piezoelectric coefficients of brittle inorganic ceramics and the lower coefficients of superior flexibility and biocompatibility of organic polymers poses a significant challenge. This work introduces a novel multilayer composite PENG, integrating a single-crystal BaTiO₃ (BTO) film between poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) layers. The PVDF-TrFE/BTO/PVDF-TrFE PENGs demonstrate substantially improved energy harvesting performance, with outputs reaching up to 15.1 V, 2.39 µA, and power density of 17.33 µW cm⁻² during bending deformation. This power density represents a significant increase compared to pure PVDF-TrFE and nanoparticle BTO-doped PVDF-TrFE PENGs. Durability tests show consistent performance, with a stable ∼15.0 V output across 2000 bending cycles. Additionally, when attached to the human body, these PENGs efficiently convert body motions into electrical responses. This work demonstrates a significant enhancement in the performance of PENGs using sandwich-structured composite of PVDF-TrFE and freestanding single-crystal BTO films, showing its potential to address the power requirements of wearable and flexible electronic devices.