Aromatic Polythiourea Dielectrics with High Energy Density, High Breakdown Strength, and Low Dielectric Loss

There is an increasing demand on dielectric materials with high electric energy density and low loss for a broad range of applications in modern electronics and electrical power systems such as hybrid electric vehicles (HEV), medical defibrillators, filters, and switched-mode power supplies. One major challenge in developing dielectric polymers is how to achieve high energy density U$_{\mathrm{e}}$ while maintaining low dielectric loss, even at very high-applied electric fields. Here we show that amorphous polar-polymers with very low impurity concentration can be promising for realizing such a dielectric polymer. Polar-polymer with high dipole moment and weak dipole coupling can provide relatively high dielectric constant for high U$_{\mathrm{e}}$, eliminate polarization and conduction losses due to weak dipolar coupling and strong polar-scattering to charge carriers. Indeed, an aromatic polythiourea thin film can maintain low loss to high fields (\textgreater 1 GV/m) with a high U$_{\mathrm{e}}$ ($\sim$ 24 J/cm$^{\mathrm{3}})$, which is very attractive for energy storage capacitors.