Carbazole/Sulfone Hybrid D-π-A-Structured Bipolar Fluorophores for High-Efficiency Blue-Violet Electroluminescence

Based on a D-pi-A structural strategy incorporating carbazole as a mild electron-donor and sulfone as an electron-acceptor with a pi-conjugation-breaking feature, two novel blue-violet emitting materials (CzS1 and CzS2) were successfully designed and synthesized. The two compounds exhibit high-efficiency fluorescent emissions of intramolecular charge-transfer transition type, with impressively high quantum yields in both solution and film states. CIEy below 0.06 and excellent current/power efficiencies up to 1.89 cd A(-1)/1.58 lm W-1 were achieved with their corresponding nondoped devices. These performances currently represent the best results for OLEDs with CIEy < 0.06. Moreover, single-carrier devices were also fabricated to demonstrate the bipolar characteristics as well as to understand the different electroluminescence performance of the two fluorophores.