First-principles study of (CsMA)NaSbX6 (MA = methylammonium; X = Cl, Br, I) organic–inorganic hybrid double perovskites for optoelectronic applications

Significant interests have been drawn to organic–inorganic hybrid double perovskites towards the commercialization of Pb-free non-toxic perovskites because of their unique optoelectronic properties compared to their inorganic counterparts. In this study, the structural, electronic and optical properties, as well as stability, of (CsMA)NaSbX6(MA = methylammonium; X = Cl, Br, I) were investigated using first-principles density functional theory (DFT). Results of the DFT method reveal that the investigated compounds have tunable bandgaps, high absorption coefficients and high refractive indices. Our findings also show that the iodide-based compound, (CsMA)NaSbI6 shows superior optoelectronic properties compared to the bromide- and chloride-based compounds, (CsMA)NaSbBr6 and (CsMA)NaSbCl6. Specifically, results of the study predict the (CsMA)NaSbI6 organic–inorganic hybrid double perovskite to be a promising candidate for optoelectronic applications due to its high absorption coefficient (on the order of 106 cm−1), dielectric constant (approx. 4.43), and refractive index (2.83) as well as the high formation energy depicting its stability. These results can be utilized for synthesis of sustainable and non-toxic optoelectronic devices.