Surfactant-induced modification in photoluminescence properties of Ce0.9-xY0.1DyxO2-δ phosphors for single host white light emitting diodes

Abstract

Dy3+/Y3+ codoped spherical ceria particles were synthesized via a sol-gel method using P123 as a surfactant. P123 amount was varied to control particle size around 70–200 nm. Photoluminescence excitation spectra of as-obtained ceria nano phosphors exhibited broadband around 280–305 nm due to O2− to Ce4+ and Dy3+ charge transfer along with several sharp peaks around 325–365 nm due to f-f transitions. Strong UV excitation showed that the current phosphors were apposite for NUV-LEDs. The emission spectra of Ce0.895Y0.1 Dy0.005O2-δ phosphors comprised 489 (blue) and 579 nm (yellow) emissions corresponding to Dy3+ f-f transitions. The increase in emission intensities with P123 concentration was observed due to enhancement in crystallinity and particle size. Low Ω2 (Judd Ofelt parameter) of 1.1 × 10−20 cm2 for Ce0.895Y0.1Dy0.005O2-δ phosphors synthesized without P123 indicated high symmetry neighboring Dy3+ ions. The increase in P123 concentration resulted in the elevation of Ω2 value, leading to asymmetry surrounding Dy3+ ions. The local environment of Dy3+ was asymmetric, which caused the electric-dipole transition to upend the magnetic-dipole transition. Hence, the blue-to-yellow emission ratio (B/Y) was varied with P123, facilitating white light emission with color-coordinate (0.38,0.34). Photoluminescenc intensity of synthesized phosphors retained 86% of initial intensity at 500K (activation energy of 0.26 eV), indicating high stability at elevated temperature. The LEDs fabricated with present phosphors exhibited a color-rendering index and correlated color temperatures around 76.3 and 6065 K, respectively. The suitable Judd-Ofelt parameters and moderate activation energy suggested the feasibility of Ce0.885Y0.1Dy0.015O2-δ phosphors for white-light-emitting diodes.