Photoluminescence Emission Studies on a Lanthanum-Doped Lead Free Double Halide Perovskite, La:Cs2SnCl6

Recent advances in bandgap engineering have increasedthe possibilityof vacancy ordered double halide perovskites (VO-DHPs), Cs2SnX6 where X = Cl, Br, I with designable optoelectronicfeatures. Doping with La3+ ions modulates the band gapfrom 3.8 to 2.7 eV, allowing a steady room temperature dual emission(PL) centered at 440 and 705 nm in Cs2SnCl6.Pristine Cs2SnCl6 and La:Cs2SnCl6 both have a crystalline cubic structure with a space symmetryof Fm3m. The cubic phase correlateswell with the Rietveld refinement. SEM analysis confirms anisotropicdevelopment with huge micrometer-sized (>10 mu m) truncatedoctahedralstructures. DFT investigations show that the insertion of La3+ ions into the crystal lattice leads to the band splitting. The presentstudy elaborates the experimental understanding of the dual PL emissionproperties of La:Cs2SnCl6 leaving a scope fordetailed theoretical study on the origin of the complex electronictransitions involving f-orbital electrons.