Polycyclic Phenazine-Derived Rigid Donors Construct Thermally Activated Delayed Fluorescence Emitters for Highly Efficient Orange Oleds with Extremely Low Roll-Off

Two new thermally activated delayed fluorescence (TADF) molecules, tBuInPz-BO and InPz-BO , are constructed via connecting novel rigid polycyclic phenazine-derived donors with oxygen-bridged boron acceptor. Both emitters exhibit fast reverse intersystem crossing rates and high photoluminescence quantum yields, owing to the high molecular structural rigidity. As a result, the orange organic light-emitting diode (OLED) fabricated with tBuInPz-BO shows a maximum external quantum efficiency (EQE max ) of 22.0% with the electroluminescence peak at 585 nm. Moreover, the device displays extremely low efficiency roll-off. At high luminance of 1000 and 10000 cd/m 2 , the EQE values still maintain a high level of 20.2% and 14.8%, respectively, achieving state-of-the-art electroluminescence performance among TADF-based orange OLEDs. This work reveals the great potential of the new phenazine-derived donors for constructing highly efficient TADF emitters