Large Spectral Shift of Mn2+Emission Due to the Shrinkage of the Crystalline Host Lattice of the Hexagonal CsCdCl3Crystals and Phase Transition

All-inorganic halide perovskite crystals are consid-ered excellent optical host lattices for various dopants to obtainwavelength-tunable emissions with ultra-broad bands even over awide spectral range. Here, a series of Mn2+-doped bulk ligand-freeCsCdCl3(CCC) perovskite crystals with a hexagonal shape andsize of about 1 millimeter (mm) have been prepared by a facilehydrothermal method. These CCC:Mn2+(CCC:Mn) crystals emitthe representative orange-red photoluminescence (PL) of Mn2+(4T1(G)-6A1(S)) in the centers of hexagonal octahedronscoordinated with six Cl-ions. Afine-tuning of the Mn2+concentration from 1 to 50 mol % Cd2+induces a substantial redshift of emission spectra from 570 to 630 nm due to the shrinkage of the crystalline host lattice, and the maximum intensity ofemission is achieved at 20 mol % Mn2+doping. A further increase in the Mn2+concentration causes a decrease of the PL intensitydue to the phase transition from CCC to CsMnCl3middot2H2O (CMCH). The strong excitation bands at 360, 370, 420, and 440 nm canmake the excitation of the emissive CCC:Mn crystals possible with ultraviolet (UV) and blue chips for application in white light-emitting diodes (WLEDs). The similarity of the Mn2+-concentration-dependent emission spectra excited by various wavelengthsindicates that there is only one type of site for Mn2+occupation in CCC.

Automated summary

In this study, Mn2+-doped ligand-free CsCdCl3 perovskite crystals were prepared by a hydrothermal method, and a redshift of emission spectra was achieved by adjusting the concentration of Mn2+. Increasing the concentration of Mn2+ resulted in a decrease of PL intensity. The crystals could be excited to emit light by UV and blue excitation bands, making them suitable for use in white light-emitting diodes.