Sensitization of Mn 2+ luminescence via efficient energy transfer to suit the application of high color rendering WLEDs.

Developing novel luminescent materials with ideal properties is an endless project, urged by growing requirements of advances in energy saving, healthy lighting and environmental friendliness. Herein, a series of ScCaOBO 3 :Ce 3+ ,Mn 2+ phosphors with excellent luminescence properties were synthesized by the high temperature solid state method. X-ray diffraction was applied to analyse the phase composition of the obtained phosphors. The morphology and dopant distribution were observed by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS), respectively. The Rietveld refinements and luminescence spectra indicate that Ce 3+ preferentially occupies the Sc 3+ site and produces a blue emission band at around 460 nm, which originates from the characteristic 5d-4f transitions, while Mn 2+ preferentially occupies the Ca 2+ site and emits red light due to its characteristic 4 T 1 ( 4 G)- 6 A 1 ( 6 S) transitions. Upon excitation at 354 nm, both Ce 3+ and Mn 2+ emissions can be obtained and further investigations evidenced that the broad and intense light emission of Mn 2+ located in the red spectral region is the result of energy transfer from Ce 3+ to Mn 2+ . Theoretical calculations reveal that the energy transfer process from Ce 3+ to Mn 2+ is of the resonance type and is governed by electric dipole-dipole interactions. Since the ScCaOBO 3 :Ce 3+ ,Mn 2+ phosphors are capable of producing broadband emissions that widely cover the blue and red spectral regions, the introduction of a green light-emitting phosphor CMA:Tb 3+ can conveniently generate high quality white light. Therefore, a white light-emitting diode device with extremely high color rendering indices, R a = 93.7 and R 9 = 91.9, was successfully obtained.