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

Abstract 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 Y 3 Al 5 O 12 :Ce 3+ (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.