Ambipolar hosts for blue TADF OLEDs: Assessment of the device performance and lifetime

Designing host materials suitable for thermally activated delayed fluorescence (TADF) based OLEDs emitting in the blue spectral range imposes great challenge, since several important factors including high compound stability, high triplet energy and balanced charge carrier mobility must be fulfilled. In attempt to address the issue, herein, we employed ambipolar hosts (ATRZ and tert-butyl modified ATRZtBu) composed of acridine donors and triazine acceptor linked in a bridgeless configuration and exhibiting triplet energies above 3 eV. The performance of blue TADF OLEDs containing the ambipolar hosts was thoroughly assessed and compared with that featuring benchmark host mCBP. A special emphasis was placed on the device operational lifetime, which was found to be at least twice as long for ATRZ device compared to the reference mCBP device. The enhanced device stability was attributed to broadened/shifted recombination zone from EML/HBL interface towards the center of EML resulting in a suppressed degradation due to the reduced triplet exciton concentration.