Evolution of Excitonic States and Localized Exciton Luminescence in Pb_1-xCd_xI₂Solid Solutions

Abstract

Emission spectra and decay characteristics of exciton luminescence in Pb 1- x Cd x I 2 solid solutions have been investigated for a wide range of the composition x . Continuous shift of the absorption edge toward higher energy with increasing x is ascribed to reduction in the band-width of the exciton associated with 6s-6p transition of Pb ions. The emission band appearing near the absorption edge of the solid solutions with x below 0.5 is attributed to the luminescence of excitons localized at various potential wells induced by the composition fluctuation. An essential change in the excited state character from the excitonic state to the excitation of Pb ion clusters is found to take place at the composition x around 0.5.