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 Y3Al5O12: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.

Photoluminescence mechanism of red emissive carbon dots from a diaminobenzoic acid isomer

“…19 Subsequently, several research groups successfully synthesized OPD-based RCDs with similar emission peaks by adding low concentrations of strong acidic reagents or other precursors, such as dopamine, ionic liquids and dicyandiamide, in the hydrothermal process. [36][37][38][39] By performing systematic and complex purification, a large amount of quinoxalino [2,3-b]phenolizine-2,3-diamine (QXPDA) molecular fluorophore was found to be present in the RCDs, accounting for 80% of the total mass. When QXPDA was attached to the surface of the carbon core and aggregated, green and blue emission was observed.…”

Recent advances in fluorescence and afterglow of CDs in matrices

“…To achieve solid-state fluorescence and afterglow, one approach is to encapsulate CDs into a matrix with a rigid structure, such as urea/melamine, 15 silica, 16 boric acid (BA), 17 inorganic salts, 18 zeolites, 19 biomass, 20 or polymers. 21 The realization and improvement of solid-state fluorescence and afterglow of CDs can be achieved through a combination of hydrogen, ionic and covalent bonding interactions and synergistic effects (Fig.…”

Intermediate aminophenol enables hectogram-scale synthesis of highly bright red carbon quantum dots under ambient conditions

“…For example, R-C-dots were synthesized at room temperature using o -phenylenediamine ( o -PDA) as the precursor. 19–22 However, the strong oxidizing agents (KClO 4 or H 2 O 2 ) used in these reactions prohibited the deep understanding of the growth mechanism of C-dots from o -PDA.…”