Phenothiazine dioxide-containing derivatives as efficient hosts for blue, green and yellow thermally activated delayed fluorescence OLEDs†
By conjugating 10-phenyl-10H-phenothiazine-5,5-dioxide (2PTO) with aromatic amine substituents (PhCz and DMACMN), three novel host materials namely 10-(9-phenyl-9H-carbazol-3-yl)-10H-phenothiazine 5,5-dioxide (3CzNPTO), (10-(4-(9H-carbazol-9-yl)phenyl)-10H-phenothiazine 5,5-dioxide (9CzNPTO) and 10-(4-(9,9-dimethylacridin-10(9H)-yl)-2,5-dimethylphenyl)-10H-phenothiazine 5,5-dioxide (DMACMNPTO) were designed and synthesized. DMACMNPTO with thermally activated delayed fluorescence (TADF) properties exhibited bipolar characteristics resulting from the completely separated HOMO/LUMO distribution. Using DMACMNPTO as a host for TADF emitters, devices showed a maximum external quantum efficiency (EQEmax), current efficiency (CEmax) and power efficiency (PEmax) of 18.3%, 33.3 cd A−1 and 37.4 lm W−1 in blue-emitting diodes, 18.6%, 49.1 cd A−1 and 47.2 lm W−1 in green-emitting diodes, and 19.1%, 59.2 cd A−1 and 66.0 lm W−1 in yellow-emitting diodes, respectively. These results corroborated the potential of phenothiazine dioxide-containing derivatives as host materials in a sequence of color TADF-OLEDs.