Multifaceted DFT analysis of defect chalcopyrite-type semiconductor ZnGa2S4: dynamic stability and thermoelectric efficiency

The drive to transform heat into electricity with peak efficiency is an essential impulse in the quest for next-generation renewable energy technologies. Defect chalcopyrite semiconductors are spearheading this research due to their exceptional heat conduction properties and promising potential as thermoelectric materials for energy conversion applications. This study offers an in-depth analysis of the structural, electronic, mechanical, and thermoelectric properties of the defect chalcopyrite-type semiconductor ZnGa₂S₄, utilizing first principles density functional theory coupled with semi-classical Boltzmann transport theory. With a direct bandgap of 2.34 eV, the band structure analysis of the optimized structure confirms that the compound exhibits intrinsic semiconducting behavior. A detailed mechanical analysis, including the elastic stiffness constants, suggests that ZnGa₂S₄ is mechanically stable, but brittle. Phonon dispersion calculations confirm the dynamic stability of the compound. The melting temperature is calculated to be 953.663 K. Additionally, the electronic thermoelectric properties are analyzed using the constant relaxation time approximation (CRTA) within the framework of Boltzmann transport theory. The analysis indicates significantly high Seebeck coefficients at increased temperatures. The lowest lattice thermal conductivity is determined to be 2.529 W m⁻¹ K⁻¹ at 900 K. The figure of merit (ZT) is found to have a peak value of 0.97 at 900 K for a hole concentration of 10¹⁸ cm⁻³. These results highlights ZnGa₂S₄ as a potential thermoelectric material, particularly suited for high-temperature applications, offering a balance between structural stability and favorable thermoelectric performance.