Synthesis and luminescent property of core/shell/shell phosphor nanocrystals

Abstract

Inorganic semiconductor nanocrystals have received a lot of attention due to their optical stability, superior luminescent properties, narrow emission bandwidths and controllable band gap. The emission wavelength can be controlled by doping various materials such as transition metal or rare-earth metal ion into single core nanocrystals. Among II-VI group, zinc sulfide is commonly used as the host lattice because of wide band gap (3.68eV), high crystallinity, non-toxic to human body unlike cadmium. Generally, synthesis of nanocrystals is toxic process because it is synthesized organic reaction with a lot of reagents at high temperature. Moreover it generates chemical waste and needs complicated post-process to get pure nanocrystals. . In this thesis, core/doped shell/shell type ZnSe/ZnS:M/ZnS nanocrystals were synthesized in aqueous phase using simple, economical, safe and low temperature process. The emission color of nanocrystals can be controlled with full color by varying dopant concentrations of Cu2+ and Mn2+ ion. We successfully obtain a blue, green, white, yellow, orange color nanocrystals and specific wavelength can measure by PL spectra. Especially white emitter can be easily produced with only single materials of co-doped nanocrystals without combining of red, green and blue emitting materials or fluorescent polymer composites. The crystal structures of core, core/doped shell and core/doped shell/shell were confirmed with three main peak corresponding to the (111), (220) and (311) as usually observed in zinc blende structure from XRD analysis. Furthermore, it can be confirmed that the dopant ion and outer shell no affects to the transformation of zinc blende structure. Also the structure of nanocrystals can be measured by analysis of binding energy using XPS and TEM image. Nanocrystals can be used in photonic device, LED, laser, bio and chemical sensor due to their excellent stability and high quantum yield.