The exciton absorption spectrum of thin films of superionic conductor CuPb₃Br₇

The absorption spectrum of CuPb₃Br₇ thin films was studied in the spectral range 2-6 eV within the temperature interval 90-500 K. The relationship of the exciton spectrum with transitions in the lead ion was established. The features associated with phase transitions γ->β (T_c1 = 159 K) and β -> α (T_c2 = 434 K) and with the disordering in the cation sublattice connected with the transition to the superionic state were found in the temperature dependence of the spectral position and half-width of the low-frequency exciton band