Structural, optical and charge density investigations on lead free Mn2+ doped Cs2NaBiCl6 double perovskite microcrystals

Improved ambient stability and the non-toxicity of lead-free halide double perovskites have rendered them tremendous research focus in the recent years. However, their large indirect bandgap's limit their optoelectronic applications. Introduction of activator transition metal ion such as Mn2+ in their lattices modifies their ab-sorption and emission spectrum. In this article, we have successfully synthesized Mn2+ doped Cs2B ' B '' Cl6 (B '= Na+, B ''=Bi3+) microcrystals by chemical reflux method. Crystallinity and morphological analysis were studied using X-ray diffraction and scanning electron microscopy respectively. The elemental analysis was carried out using Energy dispersive X-ray (EDS) and X-ray photoelectron spectroscopy. A prominent emission at 585 nm in tune with the 4T1 -> 6A1 transition of the Mn2+ ions is observed from the photoluminescence studies and carrier recombination dynamics was analysed using time resolved photoluminescence spectroscopy. Electron density distribution studies were also carried out using Maximum entropy method to understand the nature of bonding in Mn2+:Cs2NaBiCl6 double perovskites.