Lead-free and stable antimony-silver-halide double perovskite (CH3NH3)2AgSbI6

Abstract

A mixed metal organic-inorganic perovskite (CH3NH3)2AgSbI6 was developed in which pairs of the Pb(ii) atoms in traditional CH3NH3PbI3 perovskite are replaced by Sb(iii)/Ag(i) aliovalent units. We used density functional theory (DFT) calculations (the GLLB-SC method) with spin-orbit coupling corrections to predict the optical band gap of the most stable MA2AgSbI6 structure (2.00 eV). The results suggest that it is a promising light absorber. We then synthesized the double perovskite MA2AgSbI6 and confirmed its structure using X-ray diffraction (XRD). The optical band gap (1.93 eV) is in good agreement with the DFT calculations. The band positions of the material (vs. vacuum) are provided for future uses such as achieving the precise energy level alignments for potential photovoltaic applications. This perovskite material exhibits excellent stability in ambient air.