Design and Piezoelectric Energy Harvesting Properties of a Ferroelectric Cyclophosphazene Salt
Swati Deswal, Rishukumar Panday, Dipti R. Naphade, Pierre‐André Cazade, Sarah Guerin, Jan K. Zaręba, Alexander Steiner, Satishchandra Ogale, Thomas D. Anthopoulos, Ramamoorthy Boomishankar
Abstract
Abstract Cyclophosphazenes offer a robust and easily modifiable platform for a diverse range of functional systems that have found applications in a wide variety of areas. Herein, for the first time, it reports an organophosphazene‐based supramolecular ferroelectric [(PhCH 2 NH) 6 P 3 N 3 Me]I, [PMe]I . The compound crystallizes in the polar space group Pc and its thin‐film sample exhibits remnant polarization of 5 µC cm −2 . Vector piezoresponse force microscopy (PFM) measurements indicated the presence of multiaxial polarization. Subsequently, flexible composites of [PMe]I are fabricated for piezoelectric energy harvesting applications using thermoplastic polyurethane (TPU) as the matrix. The highest open‐circuit voltages of 13.7 V and the maximum power density of 34.60 µW cm −2 are recorded for the poled 20 wt.% [PMe]I/TPU device. To understand the molecular origins of the high performance of [PMe]I‐based mechanical energy harvesting devices, piezoelectric charge tensor values are obtained from DFT calculations of the single crystal structure. These indicate that the mechanical stress‐induced distortions in the [PMe]I crystals are facilitated by the high flexibility of the layered supramolecular assembly.