Bright Blue Light-Emitting Diodes Based on Well-Modified Carbon Dots by Designing Co-Host Systems to Balance Carriers' Injection

Leveraging bright and stable carbon dots (CDs) for blue light-emitting diodes (LEDs) is a prospective but challenging topic. Aggregation-caused quenching (ACQ) of CDs and device engineering of CDs-LEDs are two issues. Here, blue CDs with quantum yield of 59.75% are synthesized. Hydrogen bonds increase rigidity and facilitate luminescence, while polymer chains increase spatial resistance and resist ACQ. Then, solution-processed blue CDs-LEDs are assembled by blending CDs into poly(N-vinylcarbazole) (PVK) as light-emitting layer (EML). Furthermore, several other materials are also employed as the second host to reduce injection barrier, facilitate carriers' transport, and balance carriers' distribution. In particular, the blue CDs-LED based on the co-host system of PVK and 4-[1-[4-[bis(4-methylphenyl)amino]phenyl]cyclohexyl]-N-(3-methylphenyl)-N-(4-methylphenyl)benzenamine (TAPC) achieves a maximum brightness up to 827.60 cd m(-2). This work is a step forward for applying CDs in LEDs.