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

Recent advances in bandgap engineering have increased the possibility of vacancy ordered double halide perovskites (VO-DHPs), CsSnX where X = Cl, Br, I with designable optoelectronic features. Doping with La 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 CsSnCl. Pristine CsSnCl and La:CsSnCl both have a crystalline cubic structure with a space symmetry of 3. 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 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:CsSnCl leaving a scope for detailed theoretical study on the origin of the complex electronic transitions involving f-orbital electrons.