White Light Emissive Vitrimers for Phosphor-free Light Emitting Diode Encapsulations

Abstract

Current encapsulating materials for white light–emitting diodes (WLEDs) have some insurmountable problems of unrecyclable encapsulating materials and the toxicity of phosphors. The much more promising encapsulating materials should have two characteristics: 1) the chip can be directly encapsulated without phosphors via the luminescence of encapsulating materials, and 2) the encapsulating materials can be reprocessed for recycling. To this end, blue-light emissive vitrimers (BEVs) were first prepared from the reaction of epoxy resin with aliphatic amines, which exhibited strong blue-light emission at 365-nm excitation and fast stress relaxation without an external catalyst. To design the white-light emission, a well-designed yellow element of perylenetetracarboxylic dianhydride was grafted into the BEVs to generate white-light emissive vitrimers (WEVs). In the WEVs, a rare combination of blue- and yellow-light emissions was achieved for designing white light. When the WEV was used as an encapsulating adhesive for 365-nm LED chips without phosphors, stable white light with CIE coordination (0.30, 0.32) was successfully achieved, which provided a promising future for WLED encapsulations.