Sr2.975-xBaxCe0.025AlO4F: a Highly Efficient Green-Emitting Oxyfluoride Phosphor for Solid State White Lighting

A new, highly efficient green oxyfluoride phosphor family Sr2.975-xBaxCe0.025AlO4F (SBAF:Ce3+) has been developed as a component of solid state white light emitting diodes (LED). The phosphor emits with a maximum at 502 nm when excited by 405 nm excitation, with a quantum efficiency approaching 100%. When SBAF:Ce3+ (x = 1.0) is incorporated with encapsulant on an ultraviolet (405 nm) LED, greenish-white light with a color rendering index of 62 under a forward bias current of 20 mA is obtained. The results suggest that phosphors deriving from SBAF:Ce3+ have potential for incorporation in formulations for white LEDs and related applications. The preparation and structural and optical characterization of the phosphor family is described. Attempts to understand the origins of the high efficiency on the basis of the thermal quenching characteristics of SBAF:Ce3+ in comparison with related compounds are presented.