Structural, electronic and optical properties of lead-free antimony-copper based hybrid double perovskites for photovoltaics and optoelectronics by first principles calculations

Lead-free inorganic and organic-inorganic hybrid double perovskites are expected to be a game changer in photovoltaic technology because these compounds are stable and are free from the toxicity issues common to most lead-based halide perovskites. Herein, we investigate the electronic and optical properties of 18 potential lead-free antimony-copper based inorganic and organic-inorganic hybrid double perovskites to predict their applications in photovoltaics and optoelectronics by using first-principles density functional theory (DFT) calculation. Specifically, we evaluate the structural, electronic as well as optical properties of inorganic and hybrid double perovskites ASbCuX(6) (A = Cs-2, MA(2), FA(2), CsMA, CsFA, MAFA; X = I, Br, Cl; where, MA = CH3NH3 and FA = CH(NH2)(2)) by DFT. The investigated electronic band structures suggest that the chosen double perovskites are semiconductors with electronic band gap values ranging from 1 to 2 eV and are suitable in photovoltaic applications. In particular, the inorganic lead-free double perovskite Cs2SbCuI6 is found to have superior optical properties in comparison with other considered compounds for photovoltaic applications. In addition, the high dielectric constant, good optical absorption, high photoconductivity and small reflectivity indicate that the double perovskites have the potential to be used in diverse optoelectronic applications beyond photovoltaics.