Abstract

Intensity dependent photoluminescence spectra of quantum confined CdS_xSe_1-x nanocrystals reveal the existence of a new hot luminsecence peak coinciding with the first absorption transition. This new L₁ peak (Fig. 1) therefore corresponds to direct recombination of the photoexcited carriers (taking the weak^[1] electron-LO phonon coupling into account) and implies that the usual L₂ luminescence peak observed near the absorption edge originates from another excited state. Since, when the particle size is reduced, the relative intensity of the L₂ peak increases while that of the L₁ peak decreases, we tentatively assign this new excited state to the presence of electron and/or hole surface states. This interpretation is supported by a close examination of the absorption spectrum which shows the existence of a feature corresponding to the L₂ peak.

© 1992 IQEC