Tuning emissive characteristics of TADF emitters by fusing heterocycle with acridine as donors: Highly efficient orange to red organic emitting diodes with EQE over 20%

The development of highly efficient orange-red organic thermally activated delayed fluorescence (TADF) emitters is currently challenging. Herein, we reported two new emitters, namely, BTDMAc-NAI and BFDMAc-NAI with benzofuran and benzothiophene fused to the acridine frame. Inspiringly, the target emitters showed very different emissions from orange to pure red, with the emission peak of BTDMAc-NAI red-shifting to 650 nm. Meanwhile, these two emitters showed distinct TADF characteristics and high photoluminescence quantum yields (PLQYs). As a result, the orange-red OLED based on BFDMAc-NAI demonstrated an excellent performance with external quantum efficiency (EQE) beyond 20%. This work unveils the great potential of the fused polycycle molecular design in exploiting new orange-red TADF emitters for high-performance OLEDs.