Transfer times of electrons and holes across the interface in CdS/HgS/CdS quantum dot quantum well nanoparticles

Abstract

The electron and hole trapping times in the HgS well of a 6 nm CdS/HgS/CdS quantum dot quantum well nanoparticle were determined from the rise time of the ultrafast transient absorption in the visible and IR regions as well as the trap fluorescence when the CdS core is excited. From the 1.5 ps observed rise time of the well fluorescence (which is determined by the trapping time of the slowest carrier) and the intraband hole IR absorption (150 fs), the electron localization time is found to be 1.5 ps while that of the hole is ∼150 fs. This large difference in the observed dynamics of the electron and hole in crossing the CdS/HgS interface is discussed.