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Abstract: Ce3+ and Tb3+ co-doped Sr3AlO4F phosphors were synthesized by the conventional high temperature solid-state method. X-ray diffraction (XRD) was used to characterize the phase structure. The luminescence spectra and decay lifetime curves of Ce3+ have been measured to prove energy transfer (ET) from Ce3+ to Tb3+. Under the excitation of near-ultraviolet light, Sr3AlO4F:Ce3+,Tb3+ phosphors exhibited blue emission corresponding to the f–d transition of Ce3+ ions and green emission bands corresponding to the f–f transition of Tb3+ ions, respectively. Effective energy transfer occurred from Ce3+ to Tb3+ in Sr3AlO4F host due to the observed spectra overlap between the emission spectrum of Ce3+ ion and the excitation spectrum of Tb3+ ion. The energy transfer efficiency from Ce3+ ion to Tb3+ ion was also calculated to be 51%. Furthermore, the energy transfer from Ce3+ to Tb3+ in Sr3AlO4F host was demonstrated to be resonant type via a dipole–dipole interaction mechanism. The present Ce3+ and Tb3+ co-doped Sr3AlO4F phosphor may have potential use in the technology of white light-emitting diodes. [Copyright &y& Elsevier]

Abstract: A series of new luminescent emission-tunable phosphors Sr3Gd(PO4)3(SGP):0.006Ce3+, xMn2+ have been synthesized by a high-temperature solid-state reaction. The energy transfer from Ce3+ to Mn2+ in SGP:Ce3+/Mn2+ phosphors has been validated and demonstrated to be a resonant type via a dipole–quadrupole mechanism based on the decay lifetime data, and the critical distance (R C ) calculated by quenching concentration method and spectral overlap method are 25.24 and 24.26Å, respectively. Tuning the Ce3+/Mn2+ ratio via the energy transfer varied the emission hue of from blue to white-light and eventually to yellow. These results indicate that the developed phosphor may be promising as a single-component white-light-emitting phosphor for white LEDs. [Copyright &y& Elsevier]

Abstract: Novel Y2Si4N6C:Sm3+ phosphors for white light-emitting diodes (w-LEDs) were prepared by a carbothermal reduction and nitridation method. X-ray diffraction (XRD) and photoluminescence spectra were utilized to characterize the structure and luminescence properties of the as-synthesized phosphors. The emission spectrum obtained by excitation into 291nm contains exclusively the characteristic emission of Sm3+ at 568, 607 and 654nm which correspond to the transitions from 4G5/2 to 6H5/2, 6H7/2, and 6H9/2 of Sm3+, respectively. The strongest one is located at 607nm due to 4G5/2–6H7/2 transition of Sm3+. It was found that concentration quenching occurred as a result of dipole–dipole interaction according to Dexter''s theory. The temperature dependence of photoluminescence properties was investigated from 25 to 300°C and the prepared Y2Si4N6C:Sm3+ phosphors showed superior thermal quenching properties. [Copyright &y& Elsevier]

Abstract: An efficient broadband near-infrared (NIR) quantum cutting was demonstrated in Eu2+–Yb3+ codoped Ca9Y(PO4)7 phosphor. Upon excitation of Eu2+ ions to the 4f 65d 1 level with an ultraviolet photon at 322nm, emissions of two NIR photons at 983nm of Yb3+were achieved. The dependences of the visible and NIR emissions, the decay lifetime, the energy transfer efficiency (ETE), and the quantum efficiency (QE) on the Yb3+ doping content were investigated in detail. The results indicated that the maximum ETE and the corresponding downconversion QE can reach between 80% and 179%, respectively. [Copyright &y& Elsevier]