Multifunctional TiO ₂ ‐Graphene Hybrid Interfaces for Printable High‐Energy‐Density Polymer Thin Film Capacitor

Abstract

ABSTRACT The rapid advancement of flexible and wearable electronics demands printable thin‐film capacitors that combine high dielectric performance with scalable fabrication. However, achieving this balance in polymer dielectrics remains challenging, as enhancements in dielectric constant typically come at the expense of increased loss and reduced breakdown strength. Here, we report an interface‐engineered TiO 2 ‐decorated reduced graphene oxide (rGO‐TiO 2 ) hybrid filler for high‐performance poly(vinylidene fluoride) (PVDF) dielectric nanocomposites. In this architecture, TiO 2 nanoparticles serve as insulating barriers that prevent rGO restacking while also providing heterogeneous nucleation sites that promote crystallization. The optimized composite achieves a high dielectric constant of ∼2,620 at 1 kHz, a low loss tangent of 0.027, and a robust breakdown strength of 370 kV mm − 1 at only 0.8 wt.% filler loading. Structural and thermal analyses reveal that the hybrid filler promotes electroactive β‐phase formation, contributing to the enhanced dielectric response. Leveraging its good printability and dispersion stability, the nanocomposite is formulated as a dielectric ink for Sonoplotter‐printed micro‐capacitors, delivering a volumetric capacitance of 583.7 mF cm − 3 and an energy density of 1.82 J cm − 3 at 16.67 kV mm − 1 , demonstrating proof‐of‐concept device feasibility. This hybrid interface‐engineering strategy offers a promising route toward printable, high‐performance polymer dielectrics for integrated flexible electronics.