A single phased full color emitting pyrochlore type phosphor La2Y0.66Sn0.66Sb0.66O7: Bi3+, Eu3+ for white light emitting diode applications (WLEDs)

Abstract

The phosphor converted white light emitting diodes (pc-WLEDs) are advancing rapidly in replacing the conventional fluorescent and incandescent light sources. However, the current technology of pc-WLEDs limits their large scale indoor lighting applications due to their high correlated color temperature (CCT) and poor color rendering index (CRI). In this work, a single phased full color emitting phosphor in the pyrochlore oxide system, La₂Y_0.66Sn_0.66Sb_0.66O₇: Bi³⁺, Eu³⁺ has been developed by the high temperature ceramic route. The developed phosphors are characterized by powder X-ray diffraction, luminescence and lifetime measurements. Upon near UV excitation wavelength, the singly doped phosphor, La₂Y_0.66Sn_0.66Sb_0.66O₇: Bi³⁺ show intense blue green light in the wavelength region 400–600 nm due to the characteristic transitions (³P₁ → ¹S₀) of Bi³⁺. The emission spectral analysis suggests that there exist two luminescence centers of Bi³⁺ due to occupation of different crystallographic sites in the pyrochlore lattice of La₂Y_0.66Sn_0.66Sb_0.66O₇. The deficit of red component in the emission spectra is overcome by the Eu³⁺ co-doping in the system, La₂Y_0.66Sn_0.66Sb_0.66O₇: Bi³⁺, Eu³⁺ which results in the full color emission covering the visible spectral range up to 700 nm with broad peaks along with sharp narrow characteristic peaks of Eu³⁺. The full color emission of the La₂Y_0.66Sn_0.66Sb_0.66O₇: 0.04Bi³⁺, yEu³⁺ phosphors can be tuned by adjusting the suitable Eu³⁺ dopant concentration and using appropriate energy transfer from Bi³⁺ to Eu³⁺. The full color emitting phosphor, La₂Y_0.66Sn_0.66Sb_0.66O₇:0.04Bi³⁺, 0.06Eu³⁺ can be realized with the color coordinates (0.30, 0.36), and correlated color temperature (4383K). All these results demonstrate that La₂Y_0.66Sn_0.66Sb_0.66O₇:xBi³⁺, yEu³⁺ are potential single phased full color emitting phosphors for the development of pc-WLEDs.