Optical properties of CdSe nanoparticle films prepared by chemical deposition and sol-gel methods

CdSe nanoparticle films were prepared by chemical solution deposition and formation in a silica sol-gel matrix. X-ray powder diffraction and transmission electron microscope measurements confirmed a cubic crystallographic structure of the nanoparticles, with mean diameter varying from 4 to 20 nm. The absorption and photoluminescence spectra of the smaller crystals were strongly blue-shifted due to size quantization. This Letter focuses on the study of a non-excitonic emission band, which can be associated with surface states. The results indicate that this band involves the recombination between shallow trapped electrons and deep trapped holes, with a donor-acceptor-like recombination and are analyzed in terms of the configuration coordinate model. The CdSe nanoparticles prepared by the two different methods showed essentially the same optical behavior.