Novel Triazine-Based Donor–Acceptor Ionic Green Emitters for Nondoped Light-Emitting Electrochemical Cells

Two new ionic green-emitting D–A-type emitters were designed and synthesized with good yields. The potential of diphenyl triazine as an acceptor was utilized here to generate efficient green emitters by coupling with two derivatives of imidazole donors. The synthesized emitters exhibited excellent solubility, high luminescence in solution and solid state, high thermal stability, and good film-forming abilities. Bright green emissions were achieved by applying these emitters in a light-emitting electrochemical cell (LEC) device stack. It is noteworthy that these emitters can generate excellent light emissions without additional ions or hosts. Both emitters presented similar photophysical properties. However, the phenanthroimidazole-triazine (PhTz)-based emitter performed better in devices compared to the diphenylimidazole-triazine (BzTz)-based emitter. The nondoped LEC device with PhTz and BzTz as active materials sandwiched between air-stable electrodes exhibited green emission at 505 and 499 nm with Commission Internationale de I’Eclairage coordinates of (0.28, 0.54) and (0.27, 0.52), respectively. These triazine-based devices showed a maximum brightness of 1453 and 1048 cd/m² for PhTz and BzTz, respectively. The maximum current and power efficiencies were noted to be 2.83 cd/A and 0.63 lm/W, respectively, for the PhTz-based device and 1.72 cd/A and 0.325 lm/W, respectively, for the BzTz-based device.