ZnAl₂O₄:Eu³⁺ Nanoparticle Phosphors Co-doped with Li⁺ for Red Light-Emitting Diodes

Abstract

In recent years, rare-earth doped phosphors have gathered immense attention in the luminescence field for lighting and electronic display applications. However, the unavailability of an efficient and low-cost red phosphor is a major challenge for the widespread deployment of white light-emitting diodes (WLEDs) for practical purposes. Here we report red light-emitting Li+ co-doped ZnAl2O4:Eu3+ nanophosphors synthesized by a modified sol–gel route. These nanophosphors show excellent red emission due to the 5D0 → 7F j (j = 1, 2, 3, and 4) transition of Eu3+ ions under 394 nm excitation. Li+ co-doped ZnAl2O4:Eu3+ nanophosphors exhibit an almost 2-fold increase in photoluminescence (PL) intensity upon incorporation of the optimum amount of Li+ in the ZnAl2O4:Eu3+ matrix. Apart from that, Li+ co-doping leads to the improvement of CIE coordinates that is also reflected from the enhanced color purity offered by the co-doped nanophosphors. Steady-state as well as time-resolved PL spectra clearly reveal that addition of Li+ co-activator successfully reduces nonradiative transitions in the co-doped nanophosphors. Introduction of Li+ in Eu3+ doped ZnAl2O4 effectively neutralizes the charge imbalance problem and thus leads to a significant increase in the PL efficiency of the nanophosphors. The red LED fabricated by those co-doped nanophosphors exhibits strong red emission under a driving voltage of 3 V. Obtained results strongly highlight the bright prospect of Li+ co-doped ZnAl2O4:Eu3+ nanophosphors in the LED and display applications.

ZnAl2O4:Er3+ Upconversion Nanophosphor for SPECT Imaging and Luminescence Modulation via Defect Engineering

“…Additionally, FTIR spectra validated the formation of a cubic ZnAl 2 O 4 spinel. The Al–O symmetric bending and stretching vibrational bands were observed at 544 and 649 cm –1 , respectively, which corresponds well with the literature for AlO 6 octahedral coordination in ZnAl 2 O 4 (Figure c). , FESEM images of ZnAl 2 O 4 :1%Er 3+ and 1 mol % Bi 3+ -codoped samples are given in Figure d,e. FESEM images indicated the formation of nanoparticles with an irregular sphere-like morphology.…”

“…1c). 48,49 FESEM images of ZnAl 2 O 4 :1%Er 3+ and 1 mol % Bi 3+codoped samples are given in Figure 1d,e. FESEM images indicated the formation of nanoparticles with an irregular sphere-like morphology.…”

Organically tuned white-light emission from two zero-dimensional Cd-based hybrids

“…This low efficiency of red emission constitutes an obnoxious problem for the commercialization of lighting devices. 68–72 In the present paper, two tetrahedral zero-dimensional Cd-based hybrids CdACP and CdODA are reported. The solid-states photoluminescence measurements along with the structural studies reveal that the CdACP exhibits WLE through RTP thanks to the Br − ⋯π + interactions.…”

Challenges and Strategies to Design Phosphors for Future White Light Emitting Diodes

“…Typical commercial phosphors are either rare earth or transition metal ions doped into a stable host material (typically nitrides, borates, phosphates, aluminates) with a wide band gap that does not absorb visible light. ,− Various combinations of hosts and dopants have already been explored, providing color tunable photoluminescence with high quantum efficiency. For example, optimizing dopant concentrations, minimizing reabsorption, controlling spectral width, matching excitation spectrum of phosphor with emission of chip, uniform particle sized phosphor preparation, , and reducing nonradiative channels , are typical strategies for designing a phosphor.…”