Effect of iodine doping on the luminescent properties of the photochromic material CdBr2:Cu+

Abstract

The effect of iodine doping on the roentgenoluminescence (RL) and thermoluminescence (TL) of CdBr2:Cu+ is studied using CdBr2:(Cu+ ,I-) crystals grown by the Bridgman-Stockbarger method from melts containing 0.5 wt % CuBr and 0.15, 0.5, or 5.0 wt % CdI2. The results demonstrate that, with increasing iodine content, the RL intensity first rises and then drops; in addition, the RL band shifts from 560 to 490–510 nm. At low CdI2 levels, the TL curve shows peaks at 110, 130, 152, and 168 K, characteristic of CdBr2:Cu+. At the maximum iodine concentration, the TL curve shows a weak peak at 115 K. The TL spectrum of lightly iodine-doped crystals is dominated by the 490-nm emission, which is attributable to heteronuclear anion excitons. The formation of nI- clusters in heavily doped CdBr2:(Cu+,I-) crystals reduces the concentration of (BrI)- hetero-nuclear centers. The nature of the trapping levels responsible for the TL of the crystals is discussed.