Entropy-Boosting\nIntrinsic Elemental Disorder for\nAdvanced Thermoelectric Performance in MoSSe

Entropy\ndesign, facilitated by disorder, emerges as a crucial strategy\nfor the performance enhancement of thermoelectric materials. The characteristic\naverage multielement composition of Janus MoSSe offers an opportunity\nto introduce intrinsic elemental disorder by altering the positions\nof different atoms, thereby boosting entropy. Here, we explored the\nthermoelectric performance of the initial MoSSe and various constructed\ndisordered structures through first-principles calculations. The results\ndemonstrated that the intrinsic elemental disorder enables simultaneous\noptimization of power factor and reduction of thermal conductivity,\nwith the optimal disordered structure achieving a <i>ZT</i> of 2.89 at 700 K, approximately 10 times greater than the initial\nstructure. Atomic disorder directly induces charge disorder, decreasing\nthe polarity and enhancing the charge density of the valence band\nmaximum (VBM) to optimize conductivity. This leads to local atomic\nenergy level resonances, which significantly increase the electronic\ndensity of states, enhancing the Seebeck coefficient. Moreover, the\ndisorder considerably intensifies phonon scattering through the compression\nof phonon bandgap and the increased number of peaks for phonon density\nof states. The lowest thermal conductivity of the disordered structures\nreaches 1.02 W·m<sup>–1</sup>·K<sup>–1</sup> at 700 K. Comprehensive analyses were carried out through the examination\nof phonon lifetime, phonon group velocity, and specific heat. Finally,\nwe quantified structural disorder utilizing entropy and derived thermoelectric\nperformance optimization based on the intrinsic elemental disorder\nof the Janus materials. Our results demonstrate how control over intrinsic\nelemental disorder offers an effective avenue for tuning the performance\nof thermoelectric materials.