Tunable luminescence and energy transfer properties of KSr4(BO3)3: Dy3+, Eu3+ phosphors for near-UV warm-white LEDs

Dy3+ and Eu3+ codoped KSr4(BO3)(3) phosphors were successfully synthesized by solid-state reaction process. Under near-ultraviolet (near-UV) excitation, individual Dy3+ or Eu3+ ion activated sample exhibits characteristic emissions in their respective regions. In KSr4(BO3)(3):Dy3+, xEu(3+) phosphors, the energy transfer from Dy3+ to Eu3+ was revealed to be resonant type by dipole-dipole mechanism. And the critical distance RDy-Eu was calculated to be 13.95 A. The energy transfer efficiency of KSr4(BO3)(3): Dy3+, xEu(3+) reached about 20% when the concentration of Eu3+ was 0.035. Moreover, the emitting colors of Dy3+ and Eu3+ codoped samples can be adjusted from the edge of white area to warm white via tuning the activator (Eu3+) doped concentration. More significantly, the chromaticity coordinates (0.334, 0.351) of KSr4(BO3)(3):0.005Dy(3+), 0.015Eu(3+) sample are extremely adjacent to standard white light (033, 033). The quantum efficiency of the KSr4(BO3)(3):0.005Dy(3+), 0.015Eu(3+) phosphor with 389 nm excitation is found to be 42%, demonstrating that the obtained single-component white-emitting phosphor exhibits potential applications for solid state lighting. (C) 2016 Elsevier B.V. All rights reserved.