Zn‐doped CaTiO₃:Eu³⁺ red phosphors for enhanced photoluminescence in white LEDs by solid‐state reaction

Abstract

Zn-doped CaTiO3:Eu(3+) red phosphors for enhanced photoluminescence in white light-emitting diodes (LEDs) were synthesized by a solid-state method. The structure and morphology of the obtained phosphor samples were observed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and the impact of Ca, Zn and Eu content on their photoluminescence properties was studied. The results indicated that Zn not only participates in the formation of defects in suitable lattice matrices but also has a role in flux in the transformation from ZnO to Zn2TiO4, which is beneficial for the enhancement of photoluminescence properties. Photoluminescence test data showed that the Zn-doped phosphor is excited efficiently by near-ultraviolet (NUV) light at wavelengths around 398 nm and emits an intense red light with a broad peak around 616 nm corresponding to the (5) D0 →(7) F2 transition of Eu(3+). The intensity of this phosphor emission is three times stronger than that without Zn-doping. Furthermore, this phosphor has very good thermal stability, high color purity and a low sintered temperature, all of which suggest its potential as a promising red phosphor for white LEDs.

Synthesis and luminescence properties of cubic‐shaped Ca1‐xTiO3:Eu3+ particles

“…Many new red phosphors like rare‐earth activated tungstate, molybdate, phosphate, vanadate and titanate compounds have been explored . Among them, the calcium titanate‐based red phosphors have attracted much attention because of their excellent optical, electrical and thermal properties …”

Excited-State Dopant–Host Energy-Level Alignment: Toward a Better Understanding of the Photoluminescence Behaviors of Doped Phosphors

“…The host lattice can also be excited and transfer its excitation energy to the activator, acting as a sensitizer. − The nature of both the activator ion and the host lattice determines the absorption and emission behaviors. The most commonly used activator ions, present in relatively low concentrations, are intentionally doped rare-earth ions, − transition metal ions, − d 10 ions, − and s 2 ions. − The common lattice matrices generally are insulators, meaning they have large bandgaps. Thus, a dopant–host phosphor generally exhibit type I energy-level alignment, which favors energy transfer from the host to the activator. − In contrast, if the energy level is type II, exciton dissociation and thus photoluminescence (PL) quenching may occur, which is not desiable when designing luminescent materials.…”