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+ , x Bi 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.