科研之友
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摘要
Novel near-infrared (NIR) phosphors are in demand for light-emitting diode (LED) devices to extend their suitability for new applications and, in turn, support the sustainable and healthy development of the LED industry. The Cr3+ has been used as an activator in the development of new NIR phosphors. However, one main obstacle for the Cr3+-activated phosphors is the low luminescence efficiency due to the spin-forbidden d-d transition of Cr3+. The rare-earth (RE) huntite minerals that crystallize in the form of REM3(BO3)(4) (M = Al, Sc, Cr, Fe, Ga) have a large family of members, including the rare-earth scandium borates of RESc3(BO3)(4). Interestingly, in our research, we found that the luminescence efficiency of Cr3+ in the CeSc3(BO3)(4) host, whose quantum yield was measured at 56%, is several times higher than that in GdSc3(BO3)(4), TbSc3(BO3)(4), and LuSc3(BO3)(4) hosts. Hereby, the energy conversion and transfer in the luminescence of CeSc3(BO3)(4):Cr3+ phosphor were examined. The Stokes shift of electron energy conversion within the Cr3+ 4T2g level for the emission at 818 nm and excitation at 625 nm in CeSc3(BO3)(4) host was evaluated to be 3775.1 cm(-1), and the super-large splitting energy of the F-2(5/2) and F-2(72) sub-states of the Ce3+ 4f(1) state, about 3000 cm(-1), was found in CeSc3(BO3)(4) host. The typical electronic thermal vibration peaks were observed in the excitation spectra of CeSc3(BO3)(4):Cr3+. On this basis, the smallest phonon energy, around 347.7 cm(-1), of the CeSc3(BO3)(4) host was estimated. Finally, the energy transfer that is responsible for the far higher photoluminescence of Cr3+ in CeSc3(BO3)(4) than in other hosts was proven through the way of Ce3+ emission and Cr3+ reabsorption.
