Next-Gen II–VI Semiconductor Allotropes: Unlocking Stability and Superior Thermoelectrics via First-Principles Calculations

Group II–VI semiconductors are well-known for their wurtzite, zinc blende, and rock salt phases, which have found wide applications in optoelectronics, photovoltaics, and thermoelectrics. In this work, we investigate alternative bulk layered polymorphs of these compounds designed by modifying atomic structural arrangements to achieve anisotropic bonding characteristics and potential 2D behavior. Using first-principles density functional theory (DFT) calculations, we explore the structural, dynamical, and mechanical stabilities of these layered phases, finding them comparable to their corresponding wurtzite counterparts. Remarkably, these polymorphs exhibit intrinsic semiconducting behavior with enhanced thermoelectric performance, achieving superior figure of merit (ZT ≈ 0.98–1.02) at elevated temperatures without any external modifications. Our results suggest that these layered allotropes of II–VI semiconductors offer a promising direction for next-generation thermoelectric materials, with potential for integration into energy-harvesting interfaces and device architectures as alternatives to graphene.