Light-emitting semiconductor nanoparticles without harmful cadmium have been prepared by an aqueous solution method. They are composed of Te-added ZnSe covered with ZnS, and show high emission efficiency in a blue-color region. These nanoparticles were successfully incorporated in a glass matrix by a sol-gel method and exhibit stable emission. A novel method based on self-organization effect was also developed for dispersing nanoparticles at high concentrations in glass thin films. The brightness of the glass thin films was estimated to be approximately 30 times higher than that of the conventional phosphor having the same sample thickness.