Calcination- and Etching-Free Photolithography of Inorganic Phosphor Films Consisting of Rare Earth Ion Doped Nanoparticles on Plastic Sheets

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Abstract

It is demonstrated that patterned inorganic phosphor films consisting of rare earth ion doped nanoparticles (RE-NPs) can be fabricated on plastic sheets using calcination- and etching-free photolithography. Green up-conversion luminescence and near-infrared (NIR) fluorescence appears from the RE-NPs that are prepared from Y2O3 doped with 1 mol% Er3+ and 0.85 mol% Yb3+. The diameter of the RE-NPs is estimated to be about 300 nm using dynamic light scattering. Visible transmittance of the RE-NP film fabricated by dip-coating is more than 90%. Patterned RE-NP films are obtained by dip-coating the RE-NPs on patterned photoresist films fabricated by UV exposure through a photomask, followed by selective removal of the photoresist. Optical, fluorescence, scanning electron, atomic force, and Kelvin probe force microscopies are used for the characterization of the patterned RE-NP films. The present methodology enables fabrication of patterned RE-NP films, not only on inorganic substrates but also on plastic sheets, with low cost and material consumption.

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