The quantum-confined Stark effect of PbSe nanocrystal quantum dots ͑QDs͒ in a polymer film has been studied for the near-infrared absorption in the region of 1300-1600 nm ͑corresponding to diameters of 4.0-7.0 nm͒ by using electric field modulation spectroscopy. Electroabsorption spectra of QDs show the electric-field-induced energy shift in the exciton state, resulting in the spectral broadening given by the second derivative of the absorption spectra. It is shown that the magnitude of the change in electric dipole moment following excitation into the first exciton state increases with an increase in the size of QDs.

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.

External electric field effects on spectra and decay of photoluminescence (PL) as well as on absorption spectra were measured for CdSe nanoparticles in a poly(methyl methacrylate) (PMMA) film. Electrophotoluminescence (E-PL) spectra as well as electroabsorption spectra show a remarkable Stark shift which depends on the particle size, indicating a large electric dipole moment in the first exciton state. The E-PL spectra also show that PL of CdSe is quenched by application of electric fields, and the magnitude of the field-induced quenching becomes larger with increasing size. The PL decay profiles observed in the absence and presence of electric field show that the field-induced quenching of PL mainly originates from the field-induced decrease in population of the emitting state prepared through the relaxation from the photoexcited state.

External electric field effects on emission spectrum of a dendrimer-encapsulated gold cluster in a PVA film have been examined with electric field modulation spectroscopy. Besides the Stark shift, a field-induced quenching of the emission is observed, indicating the field-induced enhancement of the rates of nonradiative processes from the emitting state.