New bipolar derivatives with diphenylsulfone or dibenzophenone as TADF based emitters for OLEDs.

Bipolar derivatives having thermally activated delayed fluorescence (TADF) functions were synthesized by multistep synthetic procedure by using 3-(N,N -diphenylamino)-9 H -carbazole and 9-(4-(4-fluorophenylsulfonyl)phenyl)carbazole or 4-(carbazol-9-yl)-4′-fluorobenzophenone in the final step. The materials have high thermal stabilities and form molecular glasses with very high glass transition temperatures of 140 °C–143 °C. The compounds were tested in multilayer TADF based organic light emitting diodes. The most efficient green device demonstrated low turn-on voltage of 2.2 V, maximum luminance of 60155 cd/m2 and high peak efficiency values of 12.1 % (35.4 cd/A and 46.3 lm/W). The device maintained high efficiency at practical luminance levels of 100 cd/m2 and 1000 cd/m2, registering 12.1 % and 11.1 %, respectively. [Display omitted] • New derivatives with TADF functions are synthesized. • The materials demonstrate high thermal stability. • The emitters were used in OLEDs. • External quantum efficiency over 12 % was reached. [ABSTRACT FROM AUTHOR]