N,S-Induced Electronic States of Carbon Nanodots Toward White Electroluminescence

In this work, nitrogen and sulfur-doped carbon nanodots (CNDs) have been synthesized from ethylenediamine-N,N'-diacetic acid and 2,2'-(ethylenedithio) diacetic acid, respectively. The method used in this work features the use of "single" molecular precursors that contain both carbon and dopant atoms, which allows examining the effects of doping in a molecular level. The effects of doping on the electronic structure of CNDs could be examined by a series of spectroscopic measurements including UV-vis absorption and photoluminescence. It is found that doping gives rise to new light absorption and photoluminescence bands at around 500 nm. Finally, light-emitting diodes (LEDs) with the CNDs synthesized have been demonstrated to show that the electronic states induced by direct doping influence their electroluminescence. Such LEDs successfully exhibit broadband electroluminescence covering the visible light range from 500 to 700 nm, resulting in bright pure white light whose CIE (Commission Internationale d'Eclairage) coordinate is (0.2894, 0.3351).