Layered-Double-Hydroxide (LDH) pyroelectric nanogenerators

Abstract

Layered Double Hydroxides (LDHs) have outstanding properties, including straightforward fabrication and connection of high-density arrays of aligned nanostructures on almost every (e.g., large area and flexible) substrates, high surface-to-volume ratios, biocompatibility, flame retardancy and several degrees of freedom (divalent and trivalent cations, trivalent/divalent cations ratio, intercalated anions and geometries) for tuning their properties as well as their band diagrams. Nevertheless, LDH pyroelectric devices have never been reported. Here we suggest that LDHs can be ideal building blocks for pyroelectric nanogenerators because of high gradients of both composition and energy-levels, size effects and extraordinary simplicity of fabrication and tuning. For validation, we fabricated several LDH nanoplatelets pyroelectric nanogenerators and found that, without any poling, the equivalent pyroelectric coefficients can be positive, up to 150 µC/(K*m2), or negative, down to – 160 µC/(K*m2), for nanogenerators made of ZnAl LDH or MgAl LDH nanoplatelets, respectively. Beside demonstrating extremely simple and low cost pyroelectric nanogenerators, our results suggest that LDHs are outstanding candidates for high performance pyroelectric nanodevices as, first, the areas of the fabricated devices are orders of magnitude larger than the areas of the nanoplatelet-to-metal junctions and, second, the high number of degrees of freedom of LDHs leaves room for significant improvements.