Time-resolved photoluminescence studies of free excitons in CuInS2 crystals

Abstract
The time-resolved photoluminescence of free excitons in bulk single-crystal CuInS2 grown by the traveling heater method is examined. The decay of free exciton emission exhibits a double exponential curve at low temperature. The decay-time constant of the fast component increases monotonically with excitation density, whereas that of the slow component appears to be independent of excitation density. From this result, the fast and slow components are attributed to nonradiative and radiative recombination processes, respectively. The radiative lifetime of free excitons is estimated to be 320±30 ps at 10 K.