Y. Zhang, W.W. Yu
Louisiana State University in Shreveport,
Keywords: Ag2Se, quantum dot, photoluminescence
Summary:The photoluminescence lifetime of Ag2S quantum dots was measured by time-resolved photoluminescence spectroscopy. It disclosed that in the low-energy electronic structure there were two dominating emissive “in-gap” states associated with surface defect and intrinsic states, which were further confirmed by Gaussian fitting of the photoluminescence spectra. The temperature-dependent emission peak energy was fitted to extract the average phonon energy, the Huang-Rhys factor, and the excitonic acoustic phonon coupling coefficient. The relative large phonon energy and small Huang−Rhys factor were revealed, which induced the little variation of emission peak energy in the low temperature range. The photoluminescence line width increased with temperature and was analyzed based on the standard equation describing the temperature dependence of the width of the ground state exciton. The variation of both the photoluminescence peak and line broadening were mostly due to the exciton to acoustic phonon coupling. The results indicated that the variations of both the band energy and the spectrum broadening for Ag2Se quantum dots were induced by the coupling of the exciton to acoustic phonon. Moreover, the thermal escape was estimated by the quantitative comparison, which provided a direct way for investigate the internal mechanism of emission.