Today a variety of non-luminescent nano materials are used for lighting applications. Nano silica and nano alumina synthesized by flame pyrolysis are commercially available. Nano silica is a highly reactive source in the production of Si-based phosphors for fluorescent lamps or LEDs. Nano silica is also used for fluidization, adjusting tixotropy and as a scattering pigment in LEDs. A thin layer of densely packed nano silica or nano alumina between glass and phosphor layer serves as a selective UV reflector and/or a barrier to mercury diffusion /1,2/. Nano alumina is added to the phosphor layer to improve adhesion. Finally non-luminescent nano materials may be used to form a thin conformal coating around phosphor particles that protects the phosphor particles and improves the maintenance of fluorescent lamps or LEDs.
Luminescent nano materials have been the subject of extensive research in the last 15 years. The small and large organic molecules that are used in OLED and LEP displays may be viewed as nano phosphors. Their efficiency and stability, however, still excludes their use in lighting applications. Potentially more stable are inorganic nano phosphors. Widely known are the semiconducting nano phosphors such as CdSe /3/ or InP /4/, ZnS:Mn /5/, as well as rare-earth doped LaPO4:Ce,Tb /6/. We have ourselves investigated nano Y2O3:Eu in detail /7/. For particle sizes below 20 nm, the optical properties of nano phosphors change, e.g. the exciton energy increases and perhaps even more important, scattering decreases. We will discuss the use of inorganic nano phosphors in fluorescent lamps and LEDs.
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/5/ A. A. Bol et al., Phys. Rev. B 58 (1998) 15997
/6/ K. Riwotzki et al., J. Phys. Chem. B 102 (19
/7/ A. Konrad et al., J. Appl Phys. 86 (1999) 3129