Synthesis, electronic structures, and photoluminescence properties of an efficient and thermally stable red-emitting phosphor Ca(3)ZrSi(2)O(9):Eu(3+),Bi(3+) for deep UV-LEDs

A series of red-emitting Ca(3)ZrSi(2)O(9):Eu(3+),xBi(3+) phosphors was synthesized using a conventional high temperature solid-state reaction method, for the purpose of promoting the emission efficiency of Eu(3+) in a Ca(3)ZrSi(2)O(9) host. The site preference of Bi(3+) and Eu(3+) in the Ca(3)ZrSi(2)O(9) host was evaluated by formation energy. The effects of Bi(3+) on electronic structure, luminescent properties, and related mechanisms were investigated. The inner quantum yield of the optimized sample increased to 72.9% (x = 0.08) from 34.6% (x = 0) at 300 nm ultraviolet light excitation. The optimized sample (x = 0.08) also showed excellent thermal stability, and typically, 84.2% of the initial emission intensity was maintained when the temperature increased to 150 °C from 25 °C, which is much higher than that without Bi(3+) doping (70.1%). The mechanisms of emission properties and thermal stability enhancement, as well as the redshift of the charge transfer band (CTB) induced by Bi(3+) doping in the Ca(3)ZrSi(2)O(9):Eu(3+) phosphor, were discussed. This study elucidates the photoluminescence properties of Bi(3+)-doped Ca(3)ZrSi(2)O(9):Eu(3+) phosphor, and indicates that it is a promising luminescent material that can be used in ultraviolet light-emitting diodes.