Boosting the piezoelectric energy harvesting in glycine polarized array through electric field-assisted PVD

The development of self-powered micro-energy sources is critical for internet of things, wearable electronics and implantable medical devices.γ-Glycine, a biocompatible piezoelectric material, shows great application potential in this field. However, its practical use is limited by the difficulty in achieving macroscopic dipole alignment ofγ-glycine crystals. Herein, an electric field-assisted physical vapor deposition (PVD) strategy is proposed to address this challenge. By applying a continuous DC bias field during PVD crystallization, macroscopically polarizedγ-glycine arrays with uniform molecular orientation have been successfully fabricated. Systematic characterizations using XRD, SEM, and PFM confirm enhanced crystallinity,γ-phase purity, and uniform polarization orientation. Piezoelectric energy harvesters based on these arrays exhibit a maximum open-circuit voltage of 0.25 V under 40 N periodic compression-over 400% higher than devices prepared without the electric field. Density functional theory calculations further reveal that directional hydrogen bonding in the non-centrosymmetric P3₁crystal structure enhances dielectric polarization and piezoelectric response. This work is devoted to providing a scalable route to high-performance biocompatible energy harvesters and offering new insights into controlling polar orientation in molecular crystalline materials.