Novel splitting of excitation and emission spectra of K_2TiF_6:Mn~(4+) phosphors induced by graphene quantum dots

摘要

A series of K_2TiF_6:Mn~(4+)@GQDs_(ymg/mol) (KTF:0.03Mn~(4+)@GQDs_(ymg/mol), GQDs: Graphene quantum dots) was prepared by a simple coating method. Multiple enhanced effects on excitation (PLE) & emission (PL) spectra inducing by coating of GQDs are observed: (a) The intensities of PLE&PL are greatly enhanced, (b) PLE&PL spectra have large split, (c) Emission peaks of as-ν_4, as-ν_6, s-ν_4 and s-v_3 are selectively enhanced to produce four strong peaks with almost the same intensity. Furthermore, the experimental results indicate that the appearance of the strong as-ν_4 and as-ν_6 helps to improve the red light quality of the sample. The mechanism of the enhanced effects is proposed: the coordination of GQDs with Ti~(4+) and Mn~(4+) ions leads to the splitting of the crystal field, which further results to enhancement and the large splitting of PLE and PL spectra. Prototype white light-emitting diodes (WLEDs) with low correlated color temperature and high color-rendering index are obtained using the optimal sample.