New Insights into the Multiexciton Dynamics in Phase-Pure Thick-Shell CdSe/CdS Quantum Dots

The multiexciton states in semiconductor quantum dots (QDs) have obtained increasing attention because of their extensive potential applications. Here, the pump-intensity-dependent multiexciton process in phase-pure wurtzite CdSe/CdS QDs is revealed by analyzing a fast photoluminescence (PL) decay component. The experimental results show that the PL decay traces can be fitted well by a superradiance decay function. The average number of excitons per QD (⟨N⟩), obtained by fitting PL decay traces, is proportional to the power density, which is consistent with their theoretical calculations. However, the ⟨N⟩ starts to exhibit the saturation trends when the exciton number reaches about 6, which maybe result from the increased nonradiative losses of excitons at higher pump levels. The results give us deeper insights into the multiexciton dynamics process of CdSe/CdS QDs from the viewpoint of PL decay mechanism. Moreover, the fitting results are further confirmed by the multiband amplified stimulated emission m...