The Modification Strategy of Biomass-Derived Full-Color Carbon Dots and Its Applications to Warm White Light-Emitting Diodes with Ultra-High CRI-96.2

The white light-emitting diode (W-LED) is a new generation of lighting devices, and its key technology is light-emitting materials. Biomass-derived carbon dots (CDs) are expected to be favorable candidates for a new generation of environmentally friendly fluorescent materials. However, the insufficient absolute photoluminescence quantum yield (PLQY) and lack of effective emission bands of most biomass-derived CDs limit their further applications. Herein, Defatted Sichuan pepper seed, an inexpensive biowaste, was used for the raw materials of fluorescent CDs. The preparation of highly efficient panchromatic (415–650 nm) CDs by a simple one-step solvothermal method were reported. Defatted Sichuan pepper seed biowaste was used as a carbon source, and 1,4-dihydroxynaphthalene was used as a modifier to modulate the formation of conjugated domains in CDs, and the surface structures of CDs were modified in different solvents. Meanwhile, optical trichromatic CDs with high absolute PLQY (blue CDs: 82%, green CDs: 62%, and red CDs: 48%) were selected for characterization and analysis and further mixed to prepare white CDs (W-CDs). Then, the W-CDs were embedded in starch and a PVP matrix to construct solid phosphors with excellent photoluminescence (PL) thermal stability and resistance to photobleaching. The phosphors can be used as color conversion layers for light-emitting diodes (LEDs). The final packages realized blue LED (B-LED), green LED (G-LED), red LED (R-LED), and warm W-LEDs. What’s more, the R-LED shows a high color purity of 93.7%, and the W-LED exhibits a high color rendering index (CRI) of 96.2, with a color coordinate (CIE) of (0.40, 0.39). This work provides a new way for exploring biomass-derived high-efficiency CDs to build low-cost, high-performance, and environmentally friendly LED devices.