Red-emissive nanocrystals of Cs₄Mn_x Cd_1-xSb₂Cl₁₂ layered perovskites

Layered double perovskites are currently being investigated as emerging halide-based materials for optoelectronic applications. Herein, we present the synthesis of Cs₄Mn_xCd_1−xSb₂Cl₁₂ (0 ≤ x ≤ 1) nanocrystals (NCs). X-ray powder diffraction evidences the retention of the same crystal structure for all the inspected compositions; transmission electron microscopy revealed monodisperse particles with a mean size between 10.7 nm and 12.7 nm. The absorption spectra are mostly determined by transitions related to Sb³⁺, whereas Mn²⁺ induced a red emission in the 625–650 nm range. The photoluminescence emission intensity and position vary with the Mn²⁺ content and reach the maximum for the composition with x = 0.12. Finally, we demonstrate that the photoluminescence quantum yield of the latter NCs was increased from 0.3% to 3.9% through a post-synthesis treatment with ammonium thiocyanate. The present work expands the knowledge of colloidal layered double perovskite nanocrystals, stimulating future investigations of this emerging class of materials.