External Electric Field Effects on Optical Property and Excitation Dynamics of Capped CdS Quantum Dots Embedded in a Polymer Film

Abstract

Nanocomposites of benzyl mercaptan (BM)-capped cadmium sulfide (CdS) quantum dots (QDs) have been prepared and investigated by using electric field modulation spectroscopy. Applied electric fields on absorption and photoluminescence (PL) spectra as well as PL decays of BM-capped CdS QDs embedded in a poly(methyl methacrylate) (PMMA) film have revealed a field-induced alteration. Electro-photoluminescence (E-PL) exhibits field-induced quenching of photoluminescence in the presence of electric fields. The observed E-PL spectra and field-induced change in decay profile suggest that the PL intensity alternation originates from the electric field effect on emitting state population rather than PL quantum yield, probably as a result of the presence of field-assisted dissociation into hole and electron at the photoexcited state having a charge-separated character. Field-induced change in absorption spectra showed the spectral broadening caused by the stark shifts, indicating a large electric dipole moment in the...