Piezoelectric Energy Harvesting from Two-Dimensional Boron Nitride Nanoflakes

Two-dimensional (2D) piezoelectric hexagonal boron nitride nanoflakes (h-BN NFs) were synthesized by a mechanochemical exfoliation process and transferred onto an electrode line-patterned plastic substrate to characterize the energy harvesting ability of individual NFs by external stress. A single BN NF produced alternate piezoelectric output sources of ∼50 mV and ∼30 pA when deformed by mechanical bendings. The piezoelectric voltage coefficient (g₁₁) of a single BN NF was experimentally determined to be 2.35 × 10^-3 V·m·N^-1. The piezoelectric composite composed of BN NFs and an elastomer was spin-coated onto a bulk Si substrate and then transferred onto the electrode-coated plastic substrates to fabricate a BN NFs-based flexible piezoelectric energy harvester (f-PEH) which converted a piezoelectric voltage of ∼9 V, a current of ∼200 nA, and an effective output power of ∼0.3 μW. This result provides a new strategy for precisely characterizing the energy generation ability of piezoelectric nanostructures and for demonstrating f-PEH based on 2D piezomaterials.