Exploring Al- and Ga-based quaternary materials: Toward next-gen UV protection and solar efficiency

Abstract

Coper-based quaternary chalcogenides have attained popularity due to their tunable structures, electronic, and optoelectronic properties, making these materials intriguing candidates for multifunctional applications. This study investigates the electronic, optoelectronic, elastic, and thermoelectric nature of MCuGeSe₄ (M = Al, Ga) quaternary chalcogenide materials via density functional theory. The structural studies indicate that both of these compounds crystallize in the tetragonal I $\bar{4}$ space group, with GaCuGeSe₄ exhibiting better thermodynamic stability because of stronger atomic bonding. The electronic structure studies indicate that these materials possess a direct band gap in nature and have energy gap values of 1.28 eV for AlCuGeSe₄ and 1.44 eV for GaCuGeSe₄ using TB-mBJ. The density of states (DOS) investigation demonstrates significant hybridization, which correlates to charge transport and optical activity. The maximum absorption coefficients at 11.5 eV for AlCuGeSe₄ and 10.5 eV for GaCuGeSe₄, suggesting their potential for photovoltaic and optoelectronic applications. Thermoelectric studies suggest that the Seebeck coefficient improves with temperature, reaching 3.50 × 10⁻⁶ V/K in AlCuGeSe₄ and 3.20 × 10⁻⁶ V/K in GaCuGeSe₄ at 300 K. The figure of merit increases along the temperature, reaching to a value of about 0.45 for AlCuGeSe₄ and 0.29 for GaCuGeSe₄ at 650 K, implying the potential for thermoelectric applications. MCuGeSe₄ chalcogenides provide excellent electrical, optical, and thermoelectric properties, which make them ideal for photovoltaic, optoelectronic, and energy-harvesting applications.