Physical and optoelectronic properties of double halide perovskites A2CuSbX6 (A = Cs, Rb, K; X  = Cl, Br, I) based on first principles calculations

Double perovskites A2CuSbX6 (A = Cs, Rb, K; X = Cl, Br, I) have been investigated by first principles calculations. According to the tolerance factor, formation energy, binding energy and elastic stability criterion, the other materials except Cs2CuSbI6 can be judged to have mechanical and thermodynamic stability. All the materials are ductile and show potential in wearable devices. The perovskites possess indirect band structures with bandgaps as 1.163 eV, 0.850 eV, 0.305 eV, 1.140 eV and 1.123 eV for Cs2CuSbCl6, Cs2CuSbBr6, Cs2CuSbI6, Rb2CuSbCl6 and K2CuSbCl6, respectively. Compared with the other two Cl-based perovskites, K2CuSbCl6 exhibits better optoeletronic properties because of its smaller average effective mass(0.294 m0 for mh∗ and 0.201 m0 for me∗), longer carrier lifetime and higher light absorption coefficient (6.58 × 104 cm−1) in visible region. In addition, K2CuSbCl6 has a high Debye temperature which represents better stability. The results indicate that K2CuSbCl6 is an excellent candidate for photovoltaic and optoeletronic devices.