Red Fluorescent Carbon Dots with Alkyl Chain Achieving Stable Electroluminescence Via an in Situ Electric Excitation

The energy barrier between the highest occupied molecular orbital (HOMO) of the emission layer (EML) and the hole transport layer material (HTL) restricts the development of carbon dots (CDs) based light-emitting diodes (LEDs). Here, the fabrication of red fluorescent CDs (RCDs) by a one-step solvothermal method is reported. These RCDs have a photoluminescence quantum yield (PLQY) of 47.97% and a full width at half maximum (FWHM) of 26 nm. This study also shows the RCDs-based LEDs fabrication with Poly(9,9-dioctylfluorene-co-N-(4-butylphenyl) diphenylamine (TFB) as HTL. In normal case, these devices are not able to work due to the large interfacial energy barrier between RCDs and TFB. While, the RCDs-LEDs can overcome through interfacial energy barriers and achieve stable carrier injecting by a simple in situ electric excitation at the current of 50 mA cm-2. This work provides a new strategy to overcome the obstacle of mismatch of interfacial energy levels in the LEDs by an in situ electric excitation. A new strategy is provided to overcome the obstacle of mismatch of interfacial energy levels in the LEDs by an in situ electric excitation. With the continuous injection of current, the interaction of alkyl chains between RCDs and TFB is gradually enhanced to overcome interfacial energy barriers and achieve stable carrier injection.image