Red-emitting carbon dots for fabrication of high-quality white LEDs with a color rendering index of 97

Abstract

Red-emitting carbon dots (R-CDs), a novel class of environmentally benign, non-toxic, and pollution-free nanomaterials, have garnered considerable attention in the field of solid-state white light-emitting diodes (WLEDs) owing to their exceptional optical properties. Herein, we synthesized R-CDs-1 with a 671 nm emission using a simple solvent thermal method employing pyromellitic acid and 1,8-diaminonaphthalene as precursors. Structural characterization and density functional theory (DFT) simulations were employed to demonstrate that the reduction in the bandgap due to structural changes leads to a redshift in the emission spectrum of R-CDs-1. By blending R-CDs-1 with commercial phosphors, high-quality WLEDs were successfully fabricated, achieving a high color rendering index (CRI) of 97, approaching the highest reported values to date. Compared to other works, the prepared WLED exhibited a color temperature closer to natural light, offering superior performance for practical illumination. This work significantly contributes to elucidating the red emission mechanism of carbon dots and advances the application of R-CDs in the development of environmentally friendly, non-toxic, high-quality white light illumination devices.