External electric field effects on state energy and photoexcitation dynamics of water-soluble CdTe nanoparticles

External electric field effects on absorption and photoluminescence (PL) spectra of colloidal CdTe nanoparticles have been measured in a poly(vinyl alcohol) (PVA) film. The electroabsorption spectra across the first exciton band are similar in shape to the second derivative of the absorption spectra, indicating the enhancement of the electric dipole moment following the optical transition to the first exciton state. The magnitude of the enhancement has been evaluated as a function of the size of the CdTe nanoparticles. The electrophotoluminescence (E-PL) spectra show a significant quenching of PL in the presence of electric fields. The direct measurements of the field-induced change in PL decay show that the field-induced quenching of PL arises from the field-induced decreases both in lifetime and in initial population of the exciton-emitting state. The E-PL spectra also show that the application of electric fields induces a red-shift or blue-shift of the PL spectra, depending on the size of the nanoparticles. It is also shown that the PL intensity of CdTe nanoparticles in PVA increases under photoirradiation at an atmospheric condition and decreases in a vacuum condition. The present results show that the emission properties of CdTe nanoparticles can be controlled by application of external perturbation such as electric field or photoirradiation.