Reduced phonon lifetime driven low lattice thermal conductivity in Se substituted WS2 for thermoelectric applications

In this study, Se substitution in WSJ significantly influences its structural, vibrational, electrical, and thermal properties, ultimately enhancing its thermoelectric performance. The isovalent Se substitution induces lattice strain and creates a strain field, along with defects like dislocations and stacking faults, which significantly reduces phonon lifetimes (t), resulting in reduced thermal conductivity by 27 % compared to pristine WS2. The 5 % Se-substituted sample exhibits an enhanced Seebeck coefficient of 545 mu V/K at 753 K, despite a slight reduction in electrical conductivity was obtained. This balance between reduced thermal conductivity and improved Seebeck coefficient leads to a 55 % increase in thermoelectric performance compared to pristine WS2. The isovalent substitution effectively decouples thermal and electrical conductivities, optimizing phonon scattering without significantly affecting charge carrier mobility. Consequently, a maximum zT of 0.03 at 753 K is achieved in the 5 % Se-substituted WS2, positioning it as a promising material for thermoelectric applications.