Efficient heuristic approach for minimization of phonon mean free path in large-area nanostructured thin films

Phonon transport simulations are conducted to unveil the design of nanostructured thin films with the lowest thermal conductivity for enhancing thermoelectric performance. An efficient and effective optimization method that utilizes simulated annealing is realized by tuning and switching a reduction rate of annealing temperature, which is a parameter to facilitate escaping local optima during the process. The superiority of this optimization approach is confirmed by demonstrating it in nanostructured thin films of various sizes. Furthermore, the characteristics of structures with lower thermal conductivities are identified from the optimization results for each size. Based on this, a large-area nanostructured thin film, in which the simulated annealing method is computationally costly, is designed and validated by comparing it with typical nanostructured thin films as a reference.