Derivatives of Cyanonaphthyl-Substituted Phenanthroimidazole as Blue Emitters for Nondoped Organic Light-Emitting Diodes

New multifunctional blue-emissive materials with superior thermal properties, viz., 4,4'-bis(1-(4-naphthyl)-1H-phenanthro[9,10-d]imidazol-2-yl)binaphthyl (NPIBN), 4,4'-bis(1-(4-cyanonaphthyl)-1H-phenanthro[9,10-d]imidazol-2-yl)biphenyl (CNPIBP), and 4,4'-bis(1-(4-cyanonaphthyl)-1H-phenanthro[9,10-d]imidazol-2-yl)binaphthyl (CNPIBN) have been synthesized. The said molecules show high photoluminescence quantum yield (Phi(s/f): NPIBN-0.75/0.68, CNPIBP-0.85/0.76, and CNPIBN-0.90/0.88). The fabricated nondoped/doped device with CNPIBN/4,4'-bis(carbazol-9-yl)biphenyl: CNPIBN display maximum efficiencies (eta(ex) 4.96/5.4%; eta(c) 7.46/7.56 cd A(-1); eta(p) 6.85/6.91 lm W-1) at low turn-on voltage (3.5/3.8 V). Nondoped devices based on D-pi-A architecture, 4-(2-(5-(9H-carbazol-9-yl)thiophen-2-yl)-1H-phenanthro[9,10-d]imidazol-1-yl)-naphthalene-1-carbonitrile exhibit maximum efficiencies (eta(ex) 2.32%; eta(c) 4.00 cd A(-1); eta(p) 3.42 lm W-1) compared to 4-(2-(5-(4-(diphenylamino)phenyl)thiophen-2-yl)-1H-phenanthro[9,10-d]imidazol-1-yl)naphthalene-1-carbonitrile (eta(ex) 2.01%; eta(c) 3.89 cd A(-1); eta(p) 3.15 lm W-1).