  Luminescence properties of colloidal quantum dots have found applications in
imaging, light-sources, and displays. Despite wide interest, several
experimental observations from these quantum dots, such as the short lifetime
on the scale of microseconds and a zero-longitudinal optical phonon line in
low-temperature photoluminescence spectrum, remain unexplained by existing
models. Here we propose a model including the effect of solid-state environment
on luminescence by capturing coherent and incoherent interactions of band-edge
exciton with phonon modes. Our model predicts the formation of dressed states
by coupling of the exciton with a confined acoustic phonon mode, and explains
the short lifetime and the presence of the zero-longitudinal optical phonon
line in the spectrum. Accounting for the interaction of the exciton with bulk
phonon modes, the model also explains the experimentally observed
temperature-dependence of the photoluminescence decay dynamics and
temperature-dependence of the photoluminescence spectrum.
