Excitons in colloidal CuI particles dispersed in a KI crystal

We have investigated the luminescence spectra of colloidal CuI particles dispersed in a KI crystal under low- and high-density excitations of the CuI particles at low temperatures. Under the low-density excitation, we have observed the luminescence of both confined and bulk-like exciton transitions in the CuI particles with zincblende and two kinds of hexagonal structures. In the bulk-like particles with the zincblende structure, the emission line of bound excitons with small binding energy of ∼ 5 meV has been recognized. The biexciton luminescence has been observed under the high-density excitation. We discuss the origins of the various excitonic states observed in the CuI particles dispersed in the KI crystal.