Life-time resolved emission spectra in CdI2 crystals

The emission spectrum of CdI2 is composed of ultraviolet (UV), green (G) and yellow (Y and Y′) bands peaking at 3.38, 2.50, 2.16 and 2.25 eV, respectively. In order to determine the initial states of the Y- and G-luminescence, decay curves have been measured at 6 and 80 K by varying emission energy. The observed decay curves are composed of two or three exponential components. These decay components were named τ1, τ2, τ3, τ3′ and τ4. The emission spectrum for each decay component, i.e., the life-time resolved emission spectrum, was constructed from the observed decay curves. At 6 K, three bands at 2.12, 2.49 and 2.64 eV are obtained for τ1, τ2 and τ3 components, respectively. At 80 K, a dominant band for the τ4 component and a weak band for the τ3′ component appear on the same energy position at 2.25 eV. The origin of each emission band in the life-time resolved emission spectra will be briefly discussed.