Orange-emissive carbon dot phosphors for warm white light-emitting diodes with high color rendering index

Orange-emissive carbon dot (o-CDs) phosphors were prepared to reduce the correlated color temperature and increase the color rendering index of carbon dots (CDs)-based white light-emitting diode (WLED) devices. 2,7-dihydroxynaphthalene was selected as the carbon source and N, N -dimethylformamide was used as the nitrogen source to synthesize nitrogen doped o-CDs with wide and double-peak emission spectrum . Warm WLED device was designed by taking o-CDs as phosphors and excited by a UV chip. Results showed that o-CDs have a fluorescence quantum yield of 26.03%, their emission spectrum is wide enough to range from 480 to 680 nm, and show good photo and thermal stability, which is quite suitable for warm WLED phosphors. o-CDs based WLED device emits warm white light with a color coordinate of (0.41, 0.39) and a correlated color temperature of 3330 K. Compared with the current warm WLEDs devices based on CDs, their color rendering index reaches a high level, which is 91. This study provides a new idea for broadening the application of CDs in warm WLEDs that used in indoor lighting.