Microstructural analysis and optical properties of the halide double perovskite Cs2BiAgBr6 single crystals

Abstract

Single crystals of the lead-free double perovskite Cs2BiAgBr6 were grown from supersaturated solution. According to characterization by XRD and EBSD methods the perovskite's crystals are of the cubic Fm-3m symmetry with the lattice constant a = 11.20 Å. DFT calculations based on the determined crystal structure reveal that the perovskite is an indirect band gap semiconductor. The recorded low temperature (1.4 K) photoluminescence spectra demonstrate three bands. With help of the ab initio quantum-chemical modeling, the two energetically lowest bands of the spectra we assign to indirect transitions. The third band in our opinion corresponds to the direct band-to-band transition.