Structural peculiarities, point defects and luminescence in Bi-doped CsCdX3 (X = Cl, Br) single crystals

Promising luminescent CsCdX3 (X = Cl, Br) single crystals, both nominally-pure and doped with bismuth, have been studied comprehensively by X-ray diffraction, X-ray synchrotron radiation, and X-ray absorption spectroscopy. Crystal structure refinement shows vacancies in the Cs crystallographic site and partial substitution of Cd2+ ions by Bi3+ ones in both CsCdCl3 and CsCdBr3 (point defects BiCd•), which is consistent with the results of X-ray absorption spectroscopy. The assumed presence of Bi1+ ions in the Cs1+ sites of doped CsCdX3 (X = Cl, Br) crystals is not confirmed. In the photoluminescence spectra of Bi-doped CsCdCl3 and CsCdBr3 crystals, a single band in the near-IR spectral range with a maximum around 1000 nm is caused by point defects BiCd•. Photoluminescence spectra and decay kinetics of Bi-doped CsCdX3 (X = Cl, Br) indicate their promising use as luminescent materials.