Journal of Physical Studies 2(4), 567–572 (1998) DOI: https://doi.org/10.30970/jps.02.567 EXCITON–PHONON INTERACTION IN CsPbCl3(1-x)I3x (x=0…1) CRYSTALS

M. V. Kutsyk¹, S. V. Myagkota², M. S. Pidzyrailo^1
1The Ivan Franko State University of Lviv, Physical Faculty,
8 Kyrylo i Mefodii Str., Lviv, UA–290005, Ukraine
² Lviv S. Z. Gzhytskyi Veterinary Medicine Academy,
50 Pekarska Str., Lviv, UA–290010, Ukraine

The reflection spectra near the absorption edge and the photoluminescence spectra of CsPbCl$_{3(1-x)}$I$_{3x}$ solid solutions ($x$=0$…$1) in the temperature range of 4.2–80 K have been measured. There are exciton series of reflection bands for the crystals with $x$ =0; 0.33 and 0.5 at 4.2 K (2.981; 2.987 and 2.989 eV for $n=1$ respectively). For the rest of the crystals ($x$ =0.66; 1) the doublet structure takes place as a result of spin – orbit splitting ($Δ E\simeq$35 meV). The exciton binding energies and the exciton radii as well as also the band gap energies and the dielectric constants of the crystals have been determined. The exciton radius tends to diminish when the iodine ion concentration increases (10.8 \AA~for CsPbCl$_3$ and 8.0 \AA~for CsPbI$_3$). As the exciton–phonon interaction becomes stronger, the electron excitation relaxation of the investigated solid solutions leads to the emission of free exciton as well as of the bound and self–trapped one. A nearly ideal regularity of localization of the Cl$^-$ and I$^-$ ions for CsPbCl$_2$I and CsPbClI$_2$ crystals was found.

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