Nanostructuring thermoelectric materials using phononic crystals and reduction in lattice thermal conductivity

Phononic crystals (PnCs) are artificially engineered nanostructures designed to manipulate thermal transport by introducing periodic variations in material properties that scatter phonons. They offer a promising route to boost thermoelectric (TE) performance by tailoring heat flow at the nanoscale. This review analyzes how PnCs enhance the TE figure of merit ( ZT ) through selective phonon scattering, with a particular focus on reducing lattice thermal conductivity while optimizing efficient electronic transport. Particular attention is given to the effects of structural parameters, including periodicity, neck size, and film thickness, on electrical and thermal transport properties. Fabrication and characterization techniques are outlined briefly; however, the discussion centers on the structure–property relationships that dictate heat and charge transport in PnCs-engineered systems. The article concludes by highlighting current limitations and outlining research directions needed to advance PnCs-based TE devices toward practical, high-efficiency applications.