We study the excitonic dynamics of a driven quantum dot under the influenceof a phonon environment, going beyond the weak exciton-phonon couplingapproximation. By combining the polaron transform and time-local projectionoperator techniques we develop a master equation that can be valid over a muchlarger range of exciton-phonon coupling strengths and temperatures than thestandard weak-coupling approach. For the experimentally relevant parametersconsidered here, we find that the weak-coupling and polaron theories give verysimilar predictions for low temperatures (below 30 K), while at highertemperatures we begin to see discrepancies between the two. This is due to thefact that, unlike the polaron approach, the weak-coupling theory is incapableof capturing multiphonon effects, while it also does not properly account forphonon-induced renormalisation of the driving frequency. In particular, we findthat the weak-coupling theory often overestimates the damping rate whencompared to that predicted by the polaron theory. Finally, we extend our theoryto include non-Markovian effects and find that, for the parameters consideredhere, they have little bearing on the excitonic Rabi rotations when plotted asa function of pulse area.
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