Photoluminescence Emission Studies on a Lanthanum-Doped Lead Free Double Halide Perovskite, La:Cs 2 SnCl 6 .

Recent advances in bandgap engineering have increased the possibility of vacancy ordered double halide perovskites (VO-DHPs), Cs 2 SnX 6 where X = Cl, Br, I with designable optoelectronic features. Doping with La 3+ ions modulates the band gap from 3.8 to 2.7 eV, allowing a steady room temperature dual emission (PL) centered at 440 and 705 nm in Cs 2 SnCl 6 . Pristine Cs 2 SnCl 6 and La:Cs 2 SnCl 6 both have a crystalline cubic structure with a space symmetry of Fm 3 m . The cubic phase correlates well with the Rietveld refinement. SEM analysis confirms anisotropic development with huge micrometer-sized (>10 μm) truncated octahedral structures. DFT investigations show that the insertion of La 3+ ions into the crystal lattice leads to the band splitting. The present study elaborates the experimental understanding of the dual PL emission properties of La:Cs 2 SnCl 6 leaving a scope for detailed theoretical study on the origin of the complex electronic transitions involving f-orbital electrons.