Multifunctional Phenanthroimidazole Derivatives to Realize High‐Performance Deep‐Blue and White Organic Light‐Emitting Diodes

Abstract Deep blue emitters with high quantum yield, good stability, and multifunctionality are still the key technology for white organic light‐emitting diodes (WOLEDs). To address this, two multifunctional deep‐blue materials 4‐{2‐[4′‐(1,4,5‐triphenyl‐4,5‐dihydro‐1H‐imidazol‐2‐yl)‐biphenyl‐4‐yl]‐3a,11b‐dihydro‐phenanthro[9,10‐d]imidazol‐1‐yl}‐benzonitrile (CPD) and 4‐(2‐{4′‐[1‐(4‐tert‐butyl‐phenyl)‐4,5‐diphenyl‐4,5‐dihydro‐1H‐imidazol‐2‐yl]‐biphenyl‐4‐yl}‐3a,11b‐dihydro‐phenanthro[9,10‐d]imidazol‐1‐yl)‐benzonitrile (tCPD) based on phenanthroimidazole units are designed, synthesized, and characterized. Both the materials show high quantum yields and good stabilities. The deep‐blue fluorescent devices using CPD and tCPD as emitters show maximum external quantum efficiency (EQE) of 5.80% and 4.71% along with Commission Internationale de I'Eclairage (CIE) coordinates of (0.15, 0.07) and (0.15, 0.09), respectively. Two‐color based WOLEDs are demonstrated by doping Ir(MDQ)₂acac into CPD and tCPD with a low doping concentration, both devices show high EQEs of 16.4% and 16.6% and CIEs of (0.49, 0.34) and (0.48, 0.32), respectively. Furthermore, three‐color based fluorescence/phosphorescence‐WOLEDs (F/P‐WOLEDs), with reasonable exciton management, are fabricated to enhance exciton utilization and improve device performance. CPD‐based WOLED shows high efficiencies of 49.4 cd A⁻¹, 53.5 lm W⁻¹, 19.0%, and CIE coordinate of (0.46, 0.46). With the same structure, tCPD‐based device also shows high efficiencies of 40.6 cd A⁻¹, 47.2 lm W⁻¹, 19.4% along with CIE coordinate of (0.43, 0.45). These results are among the best of reported deep‐blue OLEDs and F/P‐WOLEDs.