Rational design of dibenzothiophene-based host materials for PHOLEDs

A series of systematical designed host materials based on dibenzothiophene (DBT) were synthesized. Their physical properties were comprehensively characterized and compared with classic carbazole analogues. The different electron donating abilities of DBT and carbazole play an important role in the structure-property correlations. In this report, we demonstrate that the charge transport balance of host materials can be manipulated by utilizing the less electron-donating nature of DBT with proper design. Both the experimental data and theoretical calculations indicated possible bipolar property in meta-linked materials based on DBT. Through single carrier devices, an atypical bipolar transporting property was found in m-TPDBT. The meta- and ortho-linked DBT based materials exhibit decent performance in FIrpic based PHOLEDs. The best performed m-TPDBT was used as host in white phosphorescent organic light emitting diodes (PHOLEDs). Promising results were achieved with both double and single emitting layer configurations. A maximum power efficiency of 41.0 lm W^-1 was achieved for warm white devices.