Exciton-phonon interaction and conversion of excitons from free to self-trapped states in layered metal iodide crystals under hydrostatic pressure

Exciton-phonon interaction parameters in layered metal iodide crystals, BiI 3, SbI3 and PbI2, have been estimated from the measurements of the steepnes s constants oo in the Urbach tails of absorption edge spectra under hydrost atic pressure. Luminescence from self-trapped exciton (STE) and free excito n (FE) states in these crystals has been examined under pressure. Simple bu t reasonable interpretation for the drastic change in the luminescence as w ell as in the interaction parameter values is given in terms of excitonic b and anomaly. (C) 2000 Elsevier Science B.V. All rights reserved.