Theoretical exploration of eco-friendly NbCu₃M₄ (M = S, Se, Te) compounds for optoelectronic and thermoelectric applications

The rapid depletion of natural resources highlights the urgent need for sustainable, eco-friendly energy materials. In the present work, we employ first-principles density functional theory (DFT) computations to systematically investigate the structural, electronic, mechanical, optical, thermodynamic as well as thermoelectric properties of NbCu₃M₄(M=S,Se,Te) compounds. Our computational findings reveal that these materials are thermodynamically and dynamically stable in a cubic structure. They are confirmed to be indirect band gap semiconductors, with PBE-GGA calculated band gaps ranging from 0.96 eV NbCu₃Te₄ to 1.65 eV (NbCu₃S₄). Mechanical analysis confirms their elastic stability, brittle nature (with a Pugh's ratio B/G<1.45), and covalent bonding (indicated by negative Cauchy pressures). Optical exploration demonstrates high absorption coefficients (on the order of 10⁵cm⁻¹) in the visible-UV range, suggesting potential for optoelectronic devices. Thermodynamic calculations confirm stability for high-temperature operation (up to 800 K). Thermoelectric analyses reveal promising properties, including a high peak Seebeck coefficient (1.58mV/K) and power factors that steadily increase with temperature. Taken together, these comprehensive findings identify NbCu₃M₄ compounds as promising candidates for next-generation optoelectronic and thermoelectric applications.