Solid-State, Hectogram-Scale Preparation of Red Carbon Dots as Phosphor for Energy-Transfer-Induced High-Quality White LEDs with CRI of 97.

In this study, pre-crystallization-controlled, solid-state preparation of red carbon dots (C-dots) from o-phenylenediamine on a hectogram scale with a 94% yield is reported. Highly efficient red phosphor (C-dots@MCC) is obtained by dispersing the C-dots in microcrystalline cellulose, which matched extremely well with the commercial Y3 Al5 O12 :Ce3+ (YAG) phosphor. White light-emitting diodes (WLEDs) fabricated from the two phosphors emitted warm white light with a correlated color temperature of 3845 K, CIE color coordinates of (0.38, 0.37), and an extremely high color rendering index (CRI) of 95, outperforming all the reported YAG-derived WLEDs. Furthermore, the CRI value of the WLED can be further increased to 97 after fine-tuning, which is the highest CRI for WLEDs of any C-dots derived devices reported so far. The superior performance of the WLED is attributed to a delicate energy transfer between YAG and C-dots@MCC. Most importantly, the WLED maintained excellent stabilities under varied currents, working durations, moistures, and temperatures.