Probing Exciton Move and Localization in Solution-Grown Colloidal CdSe_xS_1-x Alloyed Nanowires by Temperature- and Time-Resolved Spectroscopy

Colloidal semiconductor nanowires are interesting materials with polarized optical feature for optoelectronics devices. Previously, we observed an interesting photoluminescence enhancement in colloidal alloyed CdSe_xS_1-x nanowires. In the present work, low temperature steady-state and time-resolved photoluminescence spectra were applied to understand the photoluminescence enhancement in these CdSe_xS_1-x alloyed nanowires. The band-edge emission and surface-defect emission of alloyed CdSe_xS_1-x nanowires, observed in low temperature photoluminescence spectra, show different changing trend with the variation of their composition. Moreover, the radiative lifetime for band-edge emission and surface-defect emission reveals an opposite changing trend with the variation of temperature. These findings suggest that the variation of photoluminescence quantum yields with composition is determined by the competition between exciton move and localization. If the carriers are localized in the interior of nanowires, the migration of photoinduced excitons to their surface will be prohibited, and more probability for radiative recombination at band edge occurred.