Low-voltage multicolor electroluminescence from all-inorganic carbon dots/Si-heterostructured light-emitting diodes

Low-voltage and multicolor electroluminescent light-emitting diodes (LEDs) based upon carbon dots (CDs) are demonstrated by using simple all-inorganic CDs/Si heterostructures. Electroluminescence (EL) originations of the CDs/Si LEDs are investigated clearly without the interference of commonly used organic semiconductors. Three distinct peaks at 438, 540, and 600 nm are achieved in the EL spectra of the CDs/Si LEDs, and they are found to only originate from the CDs. Addition of a PMMA polymer does not influence the EL originations, but improves the flatness of the CD active layer, thereby enhancing the EL performance of the CDs/Si LEDs. Most strikingly, the emission threshold voltage of such all-inorganic CDs/Si LEDs is as low as 3.4 V, which is the lowest onset voltage among the CDs-based LEDs by using fluorescent CDs as the active emitter. The ultra-low driving voltage proves the feasibility of the all-inorganic CDs/Si LEDs in the future multicolor solid-state lighting applications.