Photoluminescence dynamics of energy transfer between CdS quantum dots prepared by a colloidal method

We have investigated the energy transfer process in CdS quantum dots (QDs) prepared by a colloidal method. By applying a surface-modification method, the band-edge photoluminescence (PL) is intensely observed as a main PL band. The surface-modified QDs were dispersed in polyvinyl alcohol films, where the QD solutions were variously concentrated by a factor from 1 to 250. The change of the degree of concentration corresponds to the change of a mean distance between QDs. In the 1-, 10-, and 75-times concentrated samples, the decay profiles of the band-edge PL do not depend on detection energies and exhibit a slow decay in the order of hundreds of nanosecond. On the other hand, the PL-decay profiles in the 250-times concentrated sample exhibit faster decays as compared with the dilute samples. The faster decay suggests a new decay channel due to an effective energy transfer process between CdS QDs.