This article shows results on photoluminescence measurements of Si nanocrystals embedded in a SiO2 matrix. Photoluminescence spectra were obtained as functions of both temperature (10–510 K) and excitation power (0.01–100 mW). Optical emission bands with interesting behavior as temperature was raised were observed, and a model to explain these bands considering contributions from interface states associated with SiO x and Si–O–Si units, whose emissions are located around 1.32 eV, 1.41 eV and 1.57 eV, and from quantum confinement states associated with the Si nanocrystals, was proposed.