Tunable red/ blue emitting of Ca5(PO4)3F: Eu2+, Eu3+ and remote-excited color convertor for NUV-WLED

Eu 2+ /Eu 3+ co-doped Ca 5 (PO 4 ) 3 F (FAP) phosphors with tunable color of red/blue (R/B) emission were successfully synthesized by the two-step method for potential applications in light-emitting diodes (LED). Eu 2+ (or Eu 3+ ) single-doped and Eu 2+ /Eu 3+ co-doped FAP all showed pure hexagonal FAP crystal with space group P6 3 /m, indicating the occupation of Ca sites by Eu 2+ and Eu 3+ ions. Typically, Ca 5 (PO 4 ) 3 F: Eu 2+ phosphors exhibited a broad blue emission band at 451 nm under 293 nm excitation and Ca 5 (PO 4 ) 3 F: Eu 3+ samples emitted strong orange-red light at 596 nm, 615 nm and 620 nm under 394 nm excitation. Further, Eu 2+ /Eu 3+ co-doped FAP phosphors obtained by the two-step method depicted the blue emission at 451 nm (Eu 2+ ions) and the orange-red emission (Eu 3+ ions) at 596 nm, 615 nm and 620 nm with an excitation wavelength of 365 nm (NUV). The tunable R/B ratio from 0.079 to 7.035 with various CIE chromaticity coordinate can be achieved by adjusting the recalcined temperature in the second step. Ca 5 (PO 4 ) 3 F: Eu 2+ , Eu 3+ sample can be packaged with green Lu 3 Al 5 O 12 (LuAG) phosphors by 365 nm chip (1 W) and the cold white light with CIE chromaticity coordinate (0.2815, 0.3485) (CRI: 73, CCT: 7973 K) is achieving. Based on Ca 5 (PO 4 ) 3 F: Eu 2+ , Eu 3+ and 25B 2 O 3 -10SiO 2 -35ZnO-6Li 2 O-12La 2 O 3 -12WO 3 (BS-glass) (in mol%) with strong mechanical strength as a great binder, the remote-excited color convertor (PiG: phosphor in glass) has been fabricated by screen printing technology for NUV-WLED application. Finally, by comparing the working temperature of PiG and pc-WLED at the same operating time, the working temperature of PiG was stable at 32 °C when remote excitation lighting was applied, which greatly avoided the phenomenon of “thermal quenching” for phosphors caused by high temperature under the operating of WLED. Thus, it was demonstrated that Eu 2+ and Eu 3+ co-doped Ca 5 (PO 4 ) 3 F phosphors with tunable red/blue emitting would be a highly potential candidate for NUV-WLED.