White-Light-Emitting Polymer Composite Film Based on Carbon Dots and Lanthanide Complexes

A white-light-emitting polymer composite film was designed and synthesized by using carbon dots (CDs) and lanthanide complexes as primary light emitters and skillfully embedding them into a poly(methyl methacrylate) (PMMA) matrix. The hydrophilic CDs used as blue light source were prepared and functionalized by copolymerizing with methacrylate to prevent their aggregate in the hydrophobic matrix. The lanthanide complexes Eu(DBM)3 and Tb(DBM)3 (DBM: dibenzoylmethide), in which the rare earth ions have not been fully coordinated, were fabricated and used as red and green emitters. The coordinatively unsaturated lanthanide ions could further coordinate with the oxygen atoms in the PMMA chains, which makes the complexes homogeneously dispersed in matrix as well as benefits to the energy transfer process. By adjusting the ratio of CDs, Eu(DBM)3 and Tb(DBM)3 in the matrix, the high transparent film with improved thermal stability, which prepared by a simple solution cast method, could emit pure white light (CIE coordinate located at (0.31, 0.32)) under 400 nm laser with a quantum efficiency of 16.6%. The energy transfer mechanism in the white-light-emitting material was also discussed.