^aDepartment of Physics, Riphah International University, Lahore Campus, Lahore bInstitute of Electrical, Electronics and Computer Engineering University of the Punjab

^cDepartment of Botany and Microbiology, College of Science, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia;

^dElectrical and Biological Physics, Kwangwoon University, Seoul, 01897, South Korea

Recent studies have produced stable inorganic perovskites that contain no lead, replacing lead-containing perovskites' risky and unstable properties. The present investigation thoroughly examined the electrical behavior, elastic characteristics, optical features, and transport properties of Li2CuTlZ6 (Z = Cl, Br, I) halides in order to discover potential applications. The Wien2k code was utilized to apply density functional theory (DFT) in order to clarify these physical properties. Using the generalized gradient approximation (PBEsol-GGA), we determined structural parameters through the energy optimization procedure that corresponded with the available data. Additionally, elastic parameters as well as formation energies ranging between -2.33 to - 1.39 eV were used to validate cubic durability for the two halides. Moreover, the modified Becke-Johnson (mBJ) potential successfully provided precise direct bandgap values for all halides. According to this study, the shift in anions from Cl to Br is responsible for the reduction in band gap within the infrared spectrum. Our computed optical parameter findings show that Li2CuTlCl6 and Li2CuTlBr6 halides demonstrate excellent optoelectronic efficiency with low reflection, strong optical absorption, and conductivity. The investigation clarifies that the temperature-dependent character of the materials electrical transport properties is due to their very small bandgap. These materials may find use in thermoelectric applications, as evidenced by the almost unity of the obtained figure of merit, which points to their semiconducting behaviour.