Luminescence and scintillation of PbI2 and HgI2

The luminescence spectra and scintillation decay properties of wide-bandgap semiconductors PbI2 and HgI2 have been investigated as a function of temperature in the range 10–165 K. Decay times and luminosities were measured using powder samples and crystals and a pulsed X-ray facility capable of a time resolution of ∼60 ps. In both materials, near-band-edge exciton lines and broad emission bands shifted to lower energies are observed. The X-ray excited scintillations exhibit fast (ns), nonexponential decays. The rise and decay rates of the broad emission bands decrease with increasing wavelength characteristic of donor–acceptor pair emission. With increasing temperature, the luminosities decrease much faster than the fwhm decay lifetimes. Therefore the reduction in luminosity is not due primarily to thermal quenching of the excited states but to thermally activated trapping of charge carriers on nonradiative recombination centers.