Scalable Synthesis of Green Fluorescent Carbon Dot Powders with Unprecedented Efficiency

It still remains a challenge to synthesize solid-state carbon dots (CDs) with high emission efficiency; a hurdle that has hindered the application of CDs in many fields. In this work, efficient fluorescent CDs have been prepared through a one-step microwave-assisted heating method. Experimental data show strong green emissions produced from the CD powders (CDPs), carrying an unprecedented 75.9% quantum yield due to both spatial confinement and defect reduction with the introduction of NaOH. Likewise, CDPs prepared in tens of grams at 3 min time intervals also achieve high production yields at approximate to 69.8%. Specifically, for white light-emitting devices (WLEDs) with color coordinates of 0.366 and 0.366, when fabricated by coating CDPs with commercial red-emitting phosphors on blue-emitting LED chips, it is found that the luminous efficiency reached 52.3 lm W-1. Besides, the WLEDs exhibit a high color rendering index of 93.5 and show great color chromatic stability even at a driving current of 200 mA.