Novel Red-Emitting Ba2Tb(BO3)2Cl:Eu Phosphor with Efficient Energy Transfer for Potential Application in White Light-Emitting Diodes

摘要

A novel red-emitting Ba2Tb(BO3)2Cl:Eu phosphor possessing a broad excitation band in the near-ultraviolet (n-UV) region was synthesized by the solid-state reaction. Versatile Ba2Tb(BO3)2Cl compound has a rigid open framework, which can offer two types of sites for various valence’s cations to occupy, and the coexistence of Eu2+/Eu3+ and the red-emitting luminescence from Eu3+ with the aid of efficient energy transfer of Eu2+–Eu3+(Tb3+) and Tb3+–Eu3+ have been investigated. Ba2Tb(BO3)2Cl emits green emission with the main peak around 543 nm, which originates from 5D4 → 7F5 transition of Tb3+. Ba2Tb(BO3)2Cl:Eu shows bright red emission from Eu3+ with peaks around 594, 612, and 624 nm under n-UV excitation (350–420 nm). The existence of Eu2+ can be testified by the broad-band excitation spectrum, UV–vis reflectance spectrum, X-ray photoelectron spectrum, and Eu L3-edge X-ray absorption spectrum. Decay time and time-resolved luminescence measurements indicated that the interesting luminescence behavior should be ascribed to efficient energy transfer of Eu2+–Eu3+(Tb3+) and Tb3+–Eu3+ in Ba2Tb(BO3)2Cl:Eu phosphors.