Photoluminescence properties and energy transfer in the Sm3+ and Eu3+ co-doped Ca3Bi(PO4)3 red phosphor

Abstract

Red phosphors play a vital role in improving the color quality and luminous efficiency of white light-emitting diodes (w-LED). However, it is still a challenge to develop red phosphors with higher efficiency, higher color purity, and better matching near-ultraviolet (n-UV) chips. In this paper, a series of Sm3+, Eu3+ co-doped Ca3Bi(PO4)3 (CBP) were successfully prepared by the high temperature solid-state reaction method. The crystal structure, photoluminescence properties, and energy transfer mechanism were investigated in detail. The maximum doping concentration of Eu3+ in CBP was confirmed to be 30 mol% in this research considering the structural instability with higher doping concentration. Under 393 nm n-UV excitation, CBP: 8 mol% Sm3+, 25 mol% Eu3+ phosphor exhibit excellent red-lighting emission at 612 nm with high color purity of 99.28 %. More impressively, the effective excitation wavelength of Sm3+, Eu3+ co-doped CBP phosphors is extended to 391–403 nm due to energy transfer from Sm3+ to Eu3+. Moreover, the energy transfer mechanism is rationalized through dipole–dipole interaction as indicated via decay kinetics studies. The fabricated w-LED emits white light, which has high color rendering index (CRI = 86.0) at color coordinate temperature CCT = 6985 K and luminous efficiency (66 lm/w). The phosphor shows excellent thermal stability, and the fluorescence intensity to temperature 423 K can retain 75.98 % of its initial value of room temperature. These results indicate that this phosphor with high-efficiency red-emitting is a promising candidate as a red component for n-UV LED application.