A Chiral B-N Adduct as a New Frontier in Ferroelectrics and Piezoelectric Energy Harvesting

Within the burgeoning field of electronic materials, B-N Lewis acid-base pairs, distinguished by their partial charge distribution across boron and nitrogen centers, represent an underexplored class with significant potential. These materials exhibit inherent dipoles and are excellent candidates for ferroelectricity. However, the challenge lies in achieving the optimal combination of hard-soft acid-base pairs to yield B-N adducts with stable dipoles. Herein, we present an enantiomeric pair of B-N adducts [^R/SC₆H₅CH(CH₃)NH₂BF₃] (^R/SMBA-BF₃) crystallizing in the polar monoclinic P2₁ space group. The ferroelectric measurements on ^RMBA-BF₃ gave a rectangular P-E hysteresis loop with a remnant polarization of 7.65 μC cm^-2, a value that aligns with the polarization derived from the extensive density-functional theory computations. The PFM studies on the drop-casted film of ^RMBA-BF₃ further corroborate the existence of ferroelectric domains, displaying characteristic amplitude-bias butterfly and phase-bias hysteresis loops. The piezoelectric nature of the ^RMBA-BF₃ was confirmed by its direct piezoelectric coefficient (d₃₃) value of 3.5 pC N^-1 for its pellet. The piezoelectric energy harvesting applications on the sandwich devices fabricated from the as-made crystals of ^RMBA-BF₃ gave an open circuit voltage (V_PP) of 6.2 V. This work thus underscores the untapped potential of B-N adducts in the field of piezoelectric energy harvesting.