Insights into electronic, optical and thermoelectric properties of XGe ₂ Y ₄ (X = Mo, W and Y = N, P) monolayers: A DFT study

In the next-generation nanoelectronics and energy conversion technologies, layered materials have gained a lot of interest from researchers for their multifunctional and tunable properties. In this work, we carried out first-principles investigations for the in-depth study of the structural parameters, electronic characteristics, optical response and transport properties of XGe2Y4 (X [Formula: see text] Mo, W; Y [Formula: see text] N, P). The optimized lattice parameters confirm that large radii of W over Mo and P over N cause an increase in the lattice constant and thickness of the materials. The stability of these layered materials is computed from the per-atom cohesive energies and phonon spectrum. The electronic properties confirm an indirect band gap in these materials, with a band span from 0.418[Formula: see text]eV to 1.38[Formula: see text]eV. Biaxial strain confirms the tunability of the band, leading to a transition from indirect to direct band nature and from semiconducting to metallic nature at distinct strain. The optical properties were calculated from the real and imaginary parts of the dielectric function. Further, we also computed the refractive index, extinction coefficient, and absorption coefficient. Red and blue shifts in real and imaginary parts of the dielectric function are observed with strain, confirming the tunability of these materials for optoelectronic devices. Boltzmann’s transport theory is utilized to comprehend the transport properties in the free strain as well as the strained environment.