3-(N,N-Diphenylamino)carbazole Donor Containing Bipolar Derivatives with Very High Glass Transition Temperatures as Potential TADF Emitters for OLEDs

Well-defined electroactive bipolar derivatives of new structure have been synthesized from 3-(N,N-diphenylamino)-9H-carbazole and bis(4-fluorophenyl)sulfone, 4-fluorophenylsulfone or 4,4 '-difluorobenzophenone, respectively. The full characterization of their structure is described. The amorphous materials with very high glass transition temperatures of 111-173 degrees C also possess high thermal stability, with onset decomposition temperatures of 351-398 degrees C. Some of the compounds having the best solubility were tested as the emitters dispersed in 4,4 '-bis(N-carbazolyl)-1,1 '-biphenyl (CBP) host for preparation of organic light emitting diodes (OLEDs). A device containing 15 wt% of the guest bis[4-{3-(N,N-diphenylamino)carbazol-9-yl}phenyl] sulfone demonstrated the best overall characteristics with maximum brightness exceeding 2630 cd/m(2), current efficiency of 3.2 cd/A, power efficiency of 2.2 lm/W, and external quantum efficiency exceeding 1.7% at 100 cd/m(2).

Automated summary

Well-defined electroactive bipolar derivatives of new structure have been synthesized and characterized. These amorphous materials show high glass transition temperatures and thermal stability. One of the compounds demonstrates excellent characteristics as an emitter in OLEDs.