Organic and Hybrid Organic-inorganic Two Component Ferroelectric Materials and their Energy Harvesting Applications

Abstract

Multifunctional materials exhibiting ferro- and piezoelectric properties are highly desired for their applications in modern miniature electronics. These materials play a vital role in addressing some of the current demands for renewable energy sources and are employed in converting applied mechanical stimuli into electrical outputs. Ceramic materials based on inorganic oxides are traditionally used for this purpose, but the need for high-temperature syntheses, high-voltage poling, and labor-intensive fabrication impedes their practical use in modern wearable electronics. Therefore, researchers are extensively exploring ferro- and piezoelectric materials composed of organic and hybrid organic-inorganic components. These materials offer advantages such as facile synthesis, lightweight properties, exceptional flexibility, and impressive polarization values, which make them promising alternatives for the fabrication of flexible devices. This thesis starts with a general introduction to dielectric materials and their classification into ferroelectric, piezoelectric, and pyroelectric materials. Further the design and synthesis of two-component ferro- and piezoelectric materials derived from organic, organic-inorganic hybrid ammonium salts and their consequent applications as piezoelectric nanogenerators have been discussed. We have also investigated a related two-component Borane-Amine (B-N) adduct for its ferroelectric and piezoelectric energy harvesting properties. We have synthesized several noncentrosymmetric molecules suitable for piezo- and ferroelectric studies by introducing chirality into the molecular system. Anionic subunits of tetrahedral and octahedral geometry such as BiBr52-, BF4-, and PF6- resulted in stable charge-separated ammonium salts. Compounds based on dative bonds, B-N compounds with highly electronegative fluorine atoms, have been designed and synthesized. The Ferroelectric P-E hysteresis loop measurements on these materials rendered well-resolved hysteresis loops with high remnant polarization values. As the piezoelectric coefficient is directly proportional to the electric polarization, several of these materials with high remnant polarization were employed towards the fabrication of composite piezoelectric nanogenerators with piezoelectric and non-piezoelectric polymers such as polylactic acid, thermoplastic polyurethane, and polycaprolactone. These composite devices demonstrated excellent output electromechanical responses such as output voltage, current- and power-density values under various impact forces, and load resistances. The complex and miniature device formation capabilities of these composites were again examined by utilizing additive manufacturing techniques, which not only resulted in the retention of energy harvesting outputs but also resulted in enhanced output performances. These findings emphasize the potential of small molecule-based organic and organic-inorganic hybrid ferro- and piezoelectric materials for future developments in wearable technology and self-sustaining electronic devices.