Alcohol-soluble quantum dots for photoluminescent and electroluminescent applications

Traditional solution synthesized colloidal quantum dots (QDs) capped by long-chain lipophilic ligands can be well dispersed in non-polar organic solvents, however they are not suitable for the integration in thin film devices as well as polymer matrix for further applications. We have developed general and versatile ligand exchange routes to replace the long-chain methylterminated oleylamine (OLA) on QDs’ surface with short-chain hydroxyl-terminated 6-mercaptohexanol (MCH). Such ligand exchange strategy not only altered the solubility of the QDs from conventional non-polar solvents to polar alcoholic solvents, which meet the requirement for green manufacturing, but also enhanced their solution processability, which is a crucial factor for the industrial application in display and lighting. High efficient electroluminescent device was realized using the alcohol-soluble QDs, the improvement of device performance is ascribed to decreased energy barriers and increased charge injection rate between charge transport layer and the emitting layer by the substitution of short-chain ligands. Furthermore, the alcohol-soluble QDs can be well embedded into silica via a controlled sol-gel process for on-chip type LED and a luminous efficiency up to 80.25 lm/W was achieved.