Broadband excited Na3Tb(PO4)2:Ce3+/Eu2+ green/yellow‐emitting phosphors with high color purity for LED‐based application

Abstract

AbstractTo enhance the display quality of light‐emitting diodes (LEDs), it is of great significance to exploit green/yellow‐emitting phosphors with narrow emission band, high quantum yield, and excellent color purity to satisfy the application. Herein, orthophosphate‐based green/yellow‐emitting Na3Tb(PO4)2:Ce3+/Eu2+ (NTPO:Ce3+/Eu2+) phosphors have been successfully synthesized by a facile solid‐state reaction method. The absorption band of NTPO samples was extended to the near‐ultraviolet region and the absorption efficiency was significantly improved owing to a highly efficient energy transfer from Ce3+/Eu2+ ion to Tb3+ ion in NTPO host certified by time‐resolved PL spectra. Upon 300 nm excitation, the NTPO:Ce3+ is characterized by ultra‐narrow‐band green emission of Tb3+ with an absolute quantum yield of 94.5%. Unexpectedly, NTPO:Eu2+ emits bright yellow light with a color purity of 73% as a result of the blending of green light emission from Tb3+ and red light emission from Eu3+. The thermal stability has been improved by controlling the stoichiometric ratio of Na+. The prototype white LED used yellow‐emitting NTPO:Eu2+ phosphor has higher color‐rendering index (Ra = 83.5), lower correlated color temperature (CCT = 5206 K), and closer CIE color coordinates (0.338, 0.3187) to the standard white point at (0.333, 0.333) than that used green‐emitting NTPO:Ce3+ phosphor, indicating the addition of the yellow light component improved the Ra of the trichromatic (RGB) materials.