Ultrahigh Brightness Carbon Dot–Based Blue Electroluminescent LEDs by Host–Guest Energy Transfer Emission Mechanism

Abstract Ultrahigh brightness blue carbon dot–based light‐emitting diodes (CD‐LEDs) are fabricated by a host–guest doping method with poly( N ‐vinylcarbazole) (PVK) as the host to realize the high brightness and pure emission of CD‐LEDs. Oleophylic CDs are synthesized as the dopant to obtain a wide range of doping concentration of CDs because oleophylic CDs and PVK can be well cosoluble in chlorobenzene at any doping concentration. Therefore, the CD‐LEDs emitting pure blue light that dominantly originates from CDs' emission are realized by optimizing the doping concentration. A host–guest energy transfer is the main emission mechanism for CDs. It is observed that CD‐LED also achieves a maximum luminance of 569.8 cd m −2 , which is the highest luminance compared with ever reported blue CD‐LEDs.