Solution-Processed Layered Hexagonal Boron Nitride Dielectrics: A Route toward Fabrication of High Performance Flexible Devices

Liquid phase exfoliation of hexagonal boron nitride (h-BN) has been carried out in 2-butanone, a low boiling point solvent. The h-BN dispersions have achieved concentrations of 3.9 mg mL–1, which is the highest reported to date without additives or functionalization of h-BN. Along with that, production rates of h-BN dispersions are determined. Such high concentrations and production rates of h-BN dispersions can most likely be attributed to matching of adhesive and cohesive interactions between solvent and the nanosheets along with having Hansen solubility parameters close to h-BN. Electrophoretic deposition has been employed to fabricate high quality h-BN thin films. To showcase the utility aspect of the low boiling point nature, capacitors are fabricated at low temperatures and have exhibited high areal capacitance of ∼175 nF/cm2 and invariant up to 1 MHz. Flexible h-BN capacitors are fabricated under annealing free conditions and have shown an unaltered performance even after flexing 1000 cycles. Additionally, the low boiling point aspect has enabled insights into the prevailing discrepancies of capacitance drop at high frequencies. It is interesting to note that the devices are stable for more than a month under ambient conditions owing to the hydrophobic nature of h-BN unlike traditionally used metal oxide based capacitors.