Self-host blue-emitting iridium dendrimer for solution-processed non-doped phosphorescent organic light-emitting diodes with flat efficiency roll-off and less phase segregation

Abstract

A new blue-emitting dendrimer DCzFIrpic, has been successfully designed and synthesized with an iridium-cored as triplet emitter, which is covalently attached to a carbazole dendron through a non-conjugated linkage to form a self-host system. This phosphor possesses high thermal stability (Tg = 197 °C), suitable HOMO/LUMO levels (−5.42 eV/−2.53 eV), relatively high PLQY (79%) in neat films. As a result, this dendrimer was used to form a self-host system for solution-processed non-doped PhOLEDs. The blue-emitting devices achieved a superior CEmax of 15.6 cd/A and an EQEmax of 6.4%. Moreover, it is worth noting that there is a relatively flat efficiency roll-off from the peak efficiencies to the efficiencies at the brightness of 1000 cd/m2 (decreased 1.2% and 3.0%, respectively). This is mainly caused by the less phase segregation in such self-host system, and the molecular dynamics simulations have demonstrated it. At the same time, we noticed that the CE of this non-doped device is 1.6–2.7 fold than that of doped devices at the brightness of 1000 cd/m2, which indicated that this non-doped device is much more suitable for display.