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

Abstract 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.