Shan He, Erxiang Xu, Jingkun Xu, Yuanxiang Xu, Jinqiang Tang, Yuejiao Gu, Meijuan Hu, Mengfan Guo, Huaqin Kou
Poly(vinylidene fluoride) (PVDF) thin films are attractive for miniaturized low-voltage devices, yet their nanoscale structure and growth mechanism remain elusive. This study unveils the hierarchical architecture and humidity-driven phase regulation of quasi-spherulites in PVDF thin films combining advanced scanning probe microscopies. We identify a core-dendritic structure where the β-phase forms a core with a substantial in-plane dipole component and the α-phase cross-nucleates to dominate dendrites whose dipoles preferentially aligned out of plane. Humidity governs phase distribution in two distinct regimes: under low humidity (5–29%), the β-phase concentrates in the core and grows with humidity; at elevated humidity (>29%), the β-phase appears in dendrites and γ-phase emerges in both regions. These trends arise from the interplay between vapor-driven phase separation and solvent evaporation-induced crystallization, stabilizing phases with different kinetics. Our findings offer new insight into spin-coated PVDF thin films and demonstrate humidity-based control of nanoscale phase coexistence for tunable ferroelectric properties.