Electronic Profiles, Optical Absorption, and High Thermoelectric Performance of XCu3GeSe4 (X = K, Rb, Cs): A Computational Approach

This research examines the structural, electrical, optical, thermoelectric, and elastic characteristics of XCu₃GeSe₄ (X = K, Rb, Cs) by first-principles calculations. The investigation of electronic band structure verifies the semiconducting characteristics of all three materials, with bandgap values between 0.769 and 1.365 eV. Assessments of optical properties reveal significant absorption in the visible and ultraviolet spectra, rendering these materials appropriate for optoelectronic applications. Thermoelectric study reveals that KCu₃GeSe₄ possesses the figure of merit (ZT), around 0.75 at 900 K, indicating its suitability for thermoelectric applications. The elastic properties indicate mechanical stability, with KCu₃GeSe₄ and RbCu₃GeSe₄ demonstrating superior hardness and stiffness compared to CsCu₃GeSe₄. These findings offer significant insights for optimizing these materials for energy storage, optoelectronic, and thermoelectric applications.