Derivatives of cyanonaphthyl-substituted phenanthroimidazole as blue emitters for nondoped organic light-emitting diodes

Abstract

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 (Φ 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 (ν ex 4.96/5.4%; ν c 7.46/7.56 cd A -1 ν p 6.85/6.91 lm W -1 ) at low turn-on voltage (3.5/3.8 V). Nondoped devices based on D-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 (ν ex 2.32%; ν c 4.00 cd A -1 ν 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 (ν ex 2.01%; ν c 3.89 cd A -1 ν p 3.15 lm W -1 ).