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Recombination processes in europium-doped cadmium iodide crystals

“…The luminescence intensity increases and the maximum shifts to the range 540-560 nm as the temperature is lowered to 85 K. Activation of CdI 2 with a homologous anionic dopant of Cl or Br has little effect on the light yield and spectral parameters of CdI 2 at low or high temperature [2]. Doping CdI 2 with Pb 2+ , Sn 2+ , Eu 2+ , Mn 2+ , Cu + , and Ag + does modify the spectral properties of the compound and produces effective luminophores [2][3][4][5][6][7][8][9] and photochromic materials [10].…”

Spectral and kinetic characteristics of CdI2 and CdI2:Pb scintillators

“…The complex nature of the emission bands of the activated crystals is due to the fact that luminescence of CdI 2 :Pb 2+ is created by luminescence centers that are characteristic of the matrix and that are connected with the lead impurity. At low temperatures (~90 K), the luminescence spectrum of these systems can be represented as the superposition of at least four bands with maxima at about 490-500, 540-560, 590-600, and 680-700 nm [14,15]. With x-ray excitation, the emission intensity of CdI 2 :Pb 2+ with maximum in the 570-580 nm region sharply increases as the lead impurity concentration increases, and for a dopant concentration of 1.0 mol%, it is characterized by significantly greater light yield than for CdI 2 .…”

“…Radiative annihilation of anionic excitons localized on such centers leads to the appearance of long-wavelength luminescence. Consequently, we can assume that luminescence in the region λ ≥ 620 nm and the slow component of the luminescence for the CdI 2 :Pb 2+ crystal are due to recombination of charge carriers with formation of exciton-like states in complex centers, which represent associates of intrinsic and extrinsic defects [12,14]. For high dopant concentrations, the process of substitution of the cadmium ions at the crystal lattice points becomes more likely, and then the emission with maximum in the 570-580 nm region becomes dominant.…”

“…For high dopant concentrations, the process of substitution of the cadmium ions at the crystal lattice points becomes more likely, and then the emission with maximum in the 570-580 nm region becomes dominant. Luminescence in the 570-580 nm region can be interpreted as luminescence of near-activator excitons [14,19], for which fast deactivation of the excited state is typical. At low temperatures, the contribution from luminescence of self-localized excitons increases [3].…”

“…At low temperatures, the contribution from luminescence of self-localized excitons increases [3]. Evidence in favor of such a mechanism for excitation of emission in CdI 2 :Pb 2+ is the fact that emission of the matrix in the 490 nm band, connected with excitons localized on cationic vacancies [3,14], is relatively weakly detected. An activator band in the 395-405 nm region that is identified in the absorption spectra can be interpreted as an A band, connected with electronic transitions from the due to photothermal ionization of the activator ions and the appearance of photoconductivity [8].…”