Halide-Engineered Multifunctionality in Lead-Free Cs2AlTlX6 (X = I, F) Double Perovskites: A First-Principles Study of Structural, Optoelectronic, Elastic, and Thermoelectric Properties. JPEHSS 2026, 4 (1), 932-947. https://doi.org/10.63163/jpehss.v4i1.1271.