Carbon dot-based white and yellow electroluminescent light emitting diodes with a record-breaking brightness

Abstract

First, oleophilic carbon dots (CDs) with a fluorescence quantum yield (QY) of 41% were synthesized by a one-pot microwave-assisted carbonization method. Then, CD-based electroluminescent light emitting diodes (CD-LEDs) were prepared. The impact of CD aggregation on the brightness of CD-LEDs was studied. The results show that, to some extent, with the decrease of the aggregation of the CD film, the luminescence quenching of the CD-LEDs gradually decreased, and the luminance of the CD-LEDs gradually increased. Hence, in order to improve the dispersion of CDs and reduce the aggregation of CDs and the luminescence quenching of the devices, host–guest doping was adopted to effectively improve the brightness of CD-LEDs. In this work, the yellow emission of the doped devices is mainly derived from the direct carrier trapping on CDs. Moreover, white and yellow CD-LEDs were obtained from the same oleophilic CDs by tuning the structure of the devices. The white CD-LEDs exhibit a high color rendering index (CRI) of 83 with a luminance of 455.2 cd m⁻². The yellow CD-LEDs show the maximum brightness of 339.5 cd m⁻² and excellent color stability. The results show that the luminescence quenching of CD-LEDs was resisted and the brightness of CD-LEDs was improved by using host–guest doping.