Influence of monovalent Bi⁺ doping on real composition, point defects, and photoluminescence in TlCdCl3 and TlCdI3 single crystals

The structural features and real compositions with point defects of Bi+-doped TlCdCl3 and TlCdI3 single crystals, grown by the Bridgman-Stockbarger technique, are first studied using the X-ray diffraction, X-ray synchrotron radiation, and EXAFS/XANES spectroscopy. In the structures of Bi+-doped TlCdCl3 and TlCdI3 crystals, the Cd, Cl, and I sites are found to be defect-free. The vacancies in the Tl sites and interstitial Bi atoms located in the vicinity of the Tl sites are detected in the structures of both samples. In the Bi+-doped TlCdCl3, the presence of a small amount of Bi+ ions in the Tl+ sites is possible. The correlation between photoluminescence bands and point defects in the refined structures are determined. Photoluminescence spectra and decay kinetics of the Bi+-doped TlCdCl3 and TlCdI3 demonstrate that they are attractive materials for potential applications in photonics.