This article is cited in 7 papers

Optical properties

High-energy frenkel cation exciton and specific features of its self-trapping in the CdI$_2$–PbI$_2$ crystal system

I. M. Bolesta^a, V. V. Vistovskii^a, N. V. Gloskovskaya^b, M. R. Panasyuk^a, L. I. Yaritskaya<sup>c

a</sup> Ivan Franko National University of L'viv
^b N. N. Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine
^c Lviv State University of Life Safety, Ministry of Extraordinary Situations of Ukraine, L’vov, 79000, Ukraine

Abstract: It has been shown using atomic-force microscopy that the PbI$_2$ impurity is embedded in the CdI$_2$ crystal lattice in the form of nanocrystalline inclusions. The model of a high-energy cation exciton related to the $^3P_2$ state of a free Pb$^{2+}$ ion has been considered for the impurity absorption (excitation) band at 3.23 eV. The resonance narrow photoluminescence bands with the split absorption band at 3.12 and 3.20 eV have been compared with the emission of a free Frenkel exciton. It has been demonstrated that, in the temperature range 25–45 K, there arises a self-trapped exciton state, and the main role in its formation is played by the bending vibrations of the CdI$_2$ crystal lattice. The potential barrier separating the self-trapped state from the free exciton is 23 meV. The photoluminescence band at 2.4 eV is assigned to the emission of the self-trapped high-energy cation exciton of PbI$_2$ in the CdI$_2$ crystal lattice.

Received: 11.05.2010

 English version: Physics of the Solid State, 2011, 53:4, 799–803

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