Novel Bipolar Phenanthroimidazole Derivative Design for a Nondoped Deep‐Blue Emitter with High Singlet Exciton Yields

Both the “D–A” and “two-in-one” strategies are simultaneously applied in designing deep-blue emitters. Two emitters show deep-blue emission with CIE coordinates of (0.15, 0.08) and (0.15, 0.06). Both of them exhibit excellent electro­luminescence performance, high singlet exciton yields (31%), and a small efficiency roll-off (external quantum efficiencies: less than 12% at 1000 cd m−2).