Manifestation of a thermochromic phase transition in electronic spectra of C3H7NH3CuCl3 crystals

Abstract

The temperature evolution of absorption spectra of isopropylammonium trichlorocuprate (C 3 H 7 NH 3 CuCl 3 ) crystals was investigated in the energy range 1.77-2.48 eV. It was established that the optical absorption edge was described by the Urbach rule and resulted from exciton-phonon interaction. A comparatively strong exciton-phonon interaction was associated with a band produced by self-trapped excitons. Analysis of the temperature dependences for the Urbach-rule parameters confirmed the existence of a thermochromic phase transition at 325 K.