Solvent-free synthesis of oil-soluble fluorescent carbon dots for bright photoluminescent and electroluminescent light-emitting diodes

Fluorescent carbon dots (CDs) have attracted great attention in multidisciplinary fields due to their distinctive advantages of tunable emission, low toxicity and abundant raw materials. However, it is still a big challenge to effectively applicate these CDs in electroluminescent light-emitting diodes (LEDs) due to their poor oil solubility and easy aggregation-induced quenching. Herein, an oil-soluble fluorescent CDs is designed and synthesized using triphenylamine and 4-iodophenyldiphenylamine as precursors through a solvent-free reaction. The obtained CDs (TPA-CDs) display an emission peak at 551 nm with good oil-solubility in different organic solvents. Therefore, TPA-CDs can be used as the host material of emission layer to prepare monochromatic electroluminescent LEDs with a maximum luminance of 227 cd.m(-2) and as guest material in PVK to demonstrate white light electroluminescent LED with a maximum luminance of 1503 cd.m(-2). This CDs can also be mixed well with oil soluble resin to easily assemble photoluminescent devices with a high luminous efficiency of 17.1 lm.W-1. This is the first example that solvent-free synthesized CDs are used for both photoluminescent and electroluminescent devices.