Ultrafast charge carrier dynamics in CdSe/V2O5 core/shell quantum dots

Abstract

Ultrafast transient absorption (TA) spectroscopy has been carried out to study the charge carrier dynamics of CdSe core and CdSe/V₂O₅ core/shell quantum dots (QDs). A significant redshift accompanied by broadening in the first excitonic peak was observed in the UV-Vis absorption spectra of the core/shell QDs as the shell thickness increases. This interesting observation is related to a quasi-type-II alignment characterized by the spatial separation of an electron into the core/shell and a hole into the core. The observed optical excitonic spectra have further been used to study the energetics of CdSe and charge separated states with the concept of Marcus theory and confirmed that electron transfer takes place in the Marcus inverted region (). Moreover, the growth kinetics of the CdSe core and CdSe/V₂O₅ core/shell QDs, studied with TA spectroscopy, exhibits slow electron cooling in core/shell QDs because of the de-coupling of the electronic wave functions with their hole counterpart. These exciting properties reveal a new paradigm shift from CdSe QDs to CdSe/V₂O₅ core/shell QDs for highly suitable applications in photovoltaics (PV) and optoelectronic devices.