Control of intrinsic polarity for work function modulation of polyvinylidene fluoride crystalline phases

Abstract

Ferroelectric polymers with high flexibility and inherent piezo- and pyro-electric properties have gained tremendous importance for next-generation wearable electronics. In this context, we investigate the intrinsic polarity mediated work function modulation in α-, γ-, and β-crystalline phases of a ferroelectric polymer, namely, polyvinylidene fluoride. A wide range of surface potentials (i.e., −5 to −70 V) were observed depending upon the crystalline polymorph and their surface morphologies. For example, upon nucleation of electroactive γ- and β-phases, a reduction in spherulite size is observed in comparison to its α-counterpart. Ultraviolet photoelectron spectroscopy was employed to realize the effect of surface potential on the valence bands spectrum. In particular, the work function of the non-electroactive α-phase (φα ∼ 5.09 eV) significantly increased when it is converted into the electroactive γ (φγ ∼ 5.99 eV) and β (φβ ∼ 7.39 eV) phases. The advantage of surface potential variation is shown by synergistic charge generation as a result of contact electrification of single active material-based polar interfaces with different work functions.