Eco-friendly lead-free halide double perovskites A2CuMCl6 (A = K, Rb; M = Sb, Bi): stability, thermoelectric, and optoelectronic advancements through theoretical insights

Lead-free halide A 2 CuMCl 6 (A = K, Rb; M = Sb, Bi) are analyzed for stability, thermoelectric, and optoelectronic properties. Band gaps of 1.24–1.53 eV and high zT values (≈1.05–1.00) demonstrate their potential for renewable energy and optoelectronic applications.